description: A bow adorned with nameless flowers that bears the earnest hopes of an equally nameless person.
  
  You have obtained the elegant bow known as the Windblume Ode. Inscribed in the weapon is an array of n (n ≥ 3) positive distinct integers (i.e. different, no duplicates are allowed).
  
  Find the largest subset (i.e. having the maximum number of elements) of this array such that its sum is a composite number. A positive integer x is called composite if there exists a positive integer y such that 1 < y < x and x is divisible by y.
  
  If there are multiple subsets with this largest size with the composite sum, you can output any of them. It can be proven that under the constraints of the problem such a non-empty subset always exists.
  
  Input
  
  Each test consists of multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 100). Description of the test cases follows.
  
  The first line of each test case contains an integer n (3 ≤ n ≤ 100) — the length of the array.
  
  The second line of each test case contains n distinct integers a_{1},a_{2},...,a_{n} (1 ≤ a_{i} ≤ 200) — the elements of the array.
  
  Output
  
  Each test case should have two lines of output.
  
  The first line should contain a single integer x: the size of the largest subset with composite sum. The next line should contain x space separated integers representing the indices of the subset of the initial array.
  
  Example
  
  Input
  
  
  4
  3
  8 1 2
  4
  6 9 4 2
  9
  1 2 3 4 5 6 7 8 9
  3
  200 199 198
  
  
  Output
  
  
  2
  2 1
  4
  2 1 4 3
  9
  6 9 1 2 3 4 5 7 8
  3
  1 2 3 
  
  Note
  
  In the first test case, the subset \\{a_2, a_1\} has a sum of 9, which is a composite number. The only subset of size 3 has a prime sum equal to 11. Note that you could also have selected the subset \\{a_1, a_3\} with sum 8 + 2 = 10, which is composite as it's divisible by 2.
  
  In the second test case, the sum of all elements equals to 21, which is a composite number. Here we simply take the whole array as our subset.
solution: import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.File;
  import java.io.FileReader;
  import java.io.FileWriter;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.lang.reflect.Array;
  import java.util.ArrayDeque;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedHashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.PriorityQueue;
  import java.util.Queue;
  import java.util.Random;
  import java.util.Set;
  import java.util.Stack;
  import java.util.StringTokenizer;
  import java.util.TreeSet;
  import java.util.stream.Collectors;
  
  public class Main {
      static int mod = (int) (1e9) + 7;
  
      /* ======================DSU===================== */
      static class dsu {
          static int parent[], n;// min[],value[];
          static long size[];
  
          dsu(int n) {
              parent = new int[n + 1];
              size = new long[n + 1];
              // min=new int[n+1];
              // value=new int[n+1];
              Main.dsu.n = n;
              makeSet();
          }
  
          static void makeSet() {
              for (int i = 1; i <= n; i++) {
                  parent[i] = i;
                  size[i] = 1;
                  // min[i]=i;
              }
          }
  
          static int find(int a) {
              if (parent[a] == a)
                  return a;
              else {
                  return parent[a] = find(parent[a]);// Path Compression
              }
          }
  
          static void union(int a, int b) {
              int setA = find(a);
              int setB = find(b);
              if (setA == setB)
                  return;
              if (size[setA] >= size[setB]) {
                  parent[setB] = setA;
                  size[setA] += size[setB];
              } else {
                  parent[setA] = setB;
                  size[setB] += size[setA];
              }
          }
      }
  
      /* ======================================================== */
      static class Pair<X extends Number, Y extends Number> implements Comparator<Pair> {
          X x;
          Y y;
  
          // Constructor
          public Pair(X x, Y y) {
              this.x = x;
              this.y = y;
          }
  
          public Pair() {
  
          }
  
          @Override
          public int compare(Main.Pair o1, Main.Pair o2) {
              return ((int) (o1.y.intValue() - o2.y.intValue()));// Ascending Order based on 'y'
          }
      }
  
      /* ===============================Tries================================= */
      static class TrieNode {
          private HashMap<Character, TrieNode> children = new HashMap<>();
          public int size;
          boolean endOfWord;
  
          public void putChildIfAbsent(char ch) {
              children.putIfAbsent(ch, new TrieNode());
          }
  
          public TrieNode getChild(char ch) {
              return children.get(ch);
          }
      }
  
      static private TrieNode root;
  
      public static void insert(String str) {
          TrieNode curr = root;
          for (char ch : str.toCharArray()) {
              curr.putChildIfAbsent(ch);
              curr = curr.getChild(ch);
              curr.size++;
          }
          // mark the current nodes endOfWord as true
          curr.endOfWord = true;
      }
  
      public static int search(String word) {
          TrieNode curr = root;
  
          for (char ch : word.toCharArray()) {
              curr = curr.getChild(ch);
              if (curr == null) {
                  return 0;
              }
          }
          // size contains words starting with prefix- word
          return curr.size;
      }
  
      public boolean delete(TrieNode current, String word, int index) {
          if (index == word.length()) {
              // when end of word is reached only delete if currrent.endOfWord is true.
              if (!current.endOfWord) {
                  return false;
              }
              current.endOfWord = false;
              // if current has no other mapping then return true
              return current.children.size() == 0;
          }
          char ch = word.charAt(index);
          TrieNode node = current.children.get(ch);
          if (node == null) {
              return false;
          }
          boolean shouldDeleteCurrentNode = delete(node, word, index + 1);
  
          // if true is returned then delete the mapping of character and trienode
          // reference from map.
          if (shouldDeleteCurrentNode) {
              current.children.remove(ch);
              // return true if no mappings are left in the map.
              return current.children.size() == 0;
          }
          return false;
      }
  
      /* ================================================================= */
  
      static boolean isPrime(long n) {
          if (n <= 1)
              return false;
          if (n <= 3)
              return true;
          if (n % 2 == 0 || n % 3 == 0)
              return false;
          for (long i = 5; i * i <= n; i = i + 6)
              if (n % i == 0 || n % (i + 2) == 0)
                  return false;
          return true;
      }
  
      static Pair<Integer, Integer> lowerBound(long[] a, long x) { // x is the target, returns lowerBound. If not found
                                                                   // return -1
          int l = -1, r = a.length;
          while (l + 1 < r) {
              int m = (l + r) >>> 1;
              if (a[m] == x) {
                  return new Pair<>(m, 1);
              }
              if (a[m] >= x)
                  r = m;
              else
                  l = m;
          }
          return new Pair<>(r, 0);
      }
  
      static Pair<Integer, Integer> upperBound(long[] a, long x) {// x is the target, returns upperBound. If not found
          int l = -1, r = a.length;
          while (l + 1 < r) {
              int m = (l + r) >>> 1;
              if (a[m] == x) {
                  return new Pair<>(m, 1);
              }
              if (a[m] <= x)
                  l = m;
              else
                  r = m;
          }
          return new Pair<>(l + 1, 0);
      }
  
      static long gcd(long a, long b) {
          if (a == 0)
              return b;
          return gcd(b % a, a);
      }
  
      static long lcm(long a, long b) {
          return (a * b) / gcd(a, b);
      }
  
      static long power(long x, long y) {
          long res = 1;
          while (y > 0) {
              if (y % 2 == 1)
                  res = (res * x);
              y >>= 1;
              x = (x * x);
          }
          return res;
      }
  
      public double binPow(double x, int n) {// binary exponentiation with negative power as well
          if (n == 0)
              return 1.0;
          double binPow = binPow(x, n / 2);
          if (n % 2 == 0) {
              return binPow * binPow;
          } else {
              return n > 0 ? (binPow * binPow * x) : (binPow * binPow / x);
          }
      }
  
      static long ceil(long x, long y) {
          return (x % y == 0 ? x / y : (x / y + 1));
      }
  
      /*
       * ===========Modular Operations==================
       */
      static long modPower(long x, long y, long p) {
          long res = 1;
          x = x % p;
          while (y > 0) {
              if (y % 2 == 1)
                  res = (res * x) % p;
              y = y >> 1; // y = y/2
              x = (x * x) % p;
          }
          return res;
      }
  
      static long modInverse(long n, long p) {
          return modPower(n, p - 2, p);
      }
  
      static long modAdd(long a, long b) {
          return ((a + b + mod) % mod);
      }
  
      static long modMul(long a, long b) {
          return ((a % mod) * (b % mod)) % mod;
      }
  
      static long[] fac = new long[200000 + 5];
      static long[] invFac = new long[200000 + 5];
  
      static long nCrModPFermat(int n, int r) {
          if (r == 0)
              return 1;
          // return (fac[n] * modInverse(fac[r], mod) % mod * modInverse(fac[n - r], mod)
          // % mod) % mod;
          return (fac[n] * invFac[r] % mod * invFac[n - r] % mod) % mod;
      }
  
      /*
       * ===============================================
       */
  
      static void ruffleSort(long[] a) {
          int n = a.length;
          Random r = new Random();
          for (int i = 0; i < a.length; i++) {
              int oi = r.nextInt(n);
              long temp = a[i];
              a[i] = a[oi];
              a[oi] = temp;
          }
          Arrays.sort(a);
      }
  
      static void ruffleSort(int[] a) {
          int n = a.length;
          Random r = new Random();
          for (int i = 0; i < a.length; i++) {
              int oi = r.nextInt(n);
              int temp = a[i];
              a[i] = a[oi];
              a[oi] = temp;
          }
          Arrays.sort(a);
      }
  
      static String binString32(int n) {
          StringBuilder str = new StringBuilder("");
          String bin = Integer.toBinaryString(n);
          if (bin.length() != 32) {
              for (int k = 0; k < 32 - bin.length(); k++) {
                  str.append("0");
              }
              str.append(bin);
          }
          return str.toString();
      }
  
      static class sparseTable {
          public static int st[][];
          public static int log = 4;
  
          static int func(int a, int b) {// make func as per question(here min range query)
              return (int) gcd(a, b);
          }
  
          void makeTable(int n, int a[]) {
  
              st = new int[n][log];
              for (int i = 0; i < n; i++) {
                  st[i][0] = a[i];
              }
              for (int j = 1; j < log; j++) {
                  for (int i = 0; i + (1 << j) <= n; i++) {
                      st[i][j] = func(st[i][j - 1], st[i + (1 << (j - 1))][j - 1]);
                  }
              }
          }
  
          static int query(int l, int r) {
              int length = r - l + 1;
              int k = 0;
              while ((1 << (k + 1)) <= length) {
                  k++;
              }
              return func(st[l][k], st[r - (1 << k) + 1][k]);
          }
  
          static void printTable(int n) {
              for (int j = 0; j < log; j++) {
                  for (int i = 0; i < n; i++) {
                      System.out.print(st[i][j] + " ");
                  }
                  System.out.println();
              }
          }
      }
  
      /*
       * ====================================Main=================================
       */
  
      // static int st[], a[];
  
      // static void buildTree(int treeIndex, int lo, int hi) {
      // if (hi == lo) {
      // st[treeIndex] = a[lo];
      // return;
      // }
      // int mid = (lo + hi) / 2;
      // buildTree(treeIndex * 2 + 1, lo, mid);
      // buildTree(treeIndex * 2 + 2, mid + 1, hi);
      // st[treeIndex] = merge(st[treeIndex * 2 + 1], st[treeIndex * 2 + 2]);
      // }
  
      // static void update(int treeIndex, int lo, int hi, int arrIndex, int val) {
      // if (hi == lo) {
      // st[treeIndex] = val;
      // a[arrIndex] = val;
      // return;
      // }
      // int mid = (hi + lo) / 2;
      // if (mid < arrIndex) {
      // update(treeIndex * 2 + 2, mid + 1, hi, arrIndex, val);
      // } else {
      // update(treeIndex * 2 + 1, lo, mid, arrIndex, val);
      // }
      // st[treeIndex] = merge(st[treeIndex * 2 + 1], st[treeIndex * 2 + 2]);
      // }
  
      // static int query(int treeIndex, int lo, int hi, int l, int r) {
      // if (l <= lo && r >= hi) {
      // return st[treeIndex];
      // }
      // if (l > hi || r < lo) {
      // return 0;
      // }
      // int mid = (hi + lo) / 2;
      // return query(treeIndex * 2 + 1, lo, mid, l, Math.min(mid, r));
      // }
  
      // static int merge(int a, int b) {
      // return a + b;
      // }
  
      public static long findKthPositive(long[] A, long k) {
          int l = 0, r = A.length, m;
          while (l < r) {
              m = (l + r) / 2;
              if (A[m] - 1 - m < k)
                  l = m + 1;
              else
                  r = m;
          }
          return l + k;
      }
  
      static int[] z_function(char ar[]) {
          int[] z = new int[ar.length];
          z[0] = ar.length;
          int l = 0;
          int r = 0;
          for (int i = 1; i < ar.length; i++) {
              if (r < i) {
                  l = i;
                  r = i;
                  while (r < ar.length && ar[r - l] == ar[r])
                      r++;
                  z[i] = r - l;
                  r--;
              } else {
                  int k = i - l;
                  if (z[k] < r - i + 1) {
                      z[i] = z[k];
                  } else {
                      l = i;
                      while (r < ar.length && ar[r - l] == ar[r])
                          r++;
                      z[i] = r - l;
                      r--;
                  }
              }
          }
          return z;
      }
  
      static void mergeSort(int a[]) {
          int n = a.length;
          if (n >= 2) {
              int mid = n / 2;
              int left[] = new int[mid];
              int right[] = new int[n - mid];
              for (int i = 0; i < mid; i++) {
                  left[i] = a[i];
              }
              for (int i = mid; i < n; i++) {
                  right[i - mid] = a[i];
              }
              mergeSort(left);
              mergeSort(right);
              mergeSortedArray(left, right, a);
          }
      }
  
      static void mergeSortedArray(int left[], int right[], int a[]) {
          int i = 0, j = 0, k = 0, n = left.length, m = right.length;
          while (i != n && j != m) {
              if (left[i] < right[j]) {
                  a[k++] = left[i++];
              } else {
                  a[k++] = right[j++];
              }
          }
          while (i != n) {
              a[k++] = left[i++];
          }
          while (j != m) {
              a[k++] = right[j++];
          }
      }
  
      // BINARY SEARCH
      // count of set bits in a particular position
      // suffix max array/ suffix sum array/ prefix
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
  
          public FastReader() {
              br = new BufferedReader(new InputStreamReader(System.in));
          }
  
          String next() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          double nextDouble() {
              return Double.parseDouble(next());
          }
  
          String nextLine() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
  
          int[] intArr(int n) {
              int res[] = new int[n];
              for (int i = 0; i < n; i++)
                  res[i] = nextInt();
              return res;
          }
  
          long[] longArr(int n) {
              long res[] = new long[n];
              for (int i = 0; i < n; i++)
                  res[i] = nextLong();
              return res;
          }
      }
  
      static FastReader f = new FastReader();
      static BufferedWriter w = new BufferedWriter(new OutputStreamWriter(System.out));
  
      public static void main(String args[]) throws Exception {
          int t = 1;
          t = f.nextInt();
          int tc = 1;
          // fac[0] = 1;
          // for (int i = 1; i <= 200000; i++) {
          // fac[i] = fac[i - 1] * i % mod;
          // invFac[i] = modInverse(fac[i], mod);
          // }
          while (t-- != 0) {
              int n = f.nextInt();
              int a[]=new int[n];
              a=f.intArr(n);
              int sum=0;
              ArrayList<Integer> odds,evens;
              odds=new ArrayList<>();
              evens=new ArrayList<>();
              for(int i=0;i<n;i++){
                  sum+=a[i];
                  if(a[i]%2==0){
                      evens.add(i);
                  }else{
                      odds.add(i);
                  }
              }
              
              if(!isPrime(sum)){
                  w.write(n+"\n");
                  for(int i=1;i<=n;i++){
                      w.write(i+" ");
                  }
                  w.write("\n");
              }else{
                  for(int i=0;i<n;i++){
                      if(!isPrime(sum-a[i])){
                          w.write((n-1)+"\n");
                          for(int j=0;j<n;j++){
                              if(i!=j){
                                  w.write((j+1)+" ");
                              }
                          }
                          w.write("\n");
                          break;
                      }
                  }
              }
          }
          w.flush();
      }
  }
  /*
   */