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.util.*;
  import java.lang.*;
  import java.io.*;
  
  public class Main
  {
      static long mod = (int)1e9+7;
      // static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		FastReader sc =new FastReader();
  		
  	    int t=sc.nextInt();
  	    
  	   // int t=1;
  	    
  	    while(t-->0)
  	    {
  	        int n=sc.nextInt();
  	        int arr[] = sc.readArray(n);
  	        int sum = 0;
  	        
  	        for(int x:arr)
  	        {
  	            sum += x;
  	        }
  	        if(isPrime(sum) == false)
  	        {
  	            System.out.println(n);
  	            for(int i=1;i<=n;i++)
  	            {
  	                System.out.print(i+" ");
  	            }
  	            System.out.println();
  	        }
  	        else
  	        {
  	            System.out.println(n - 1);
  	            int posi = -1;
  	            for(int i=n-1;i>=0;i--)
  	            {
  	                
  	                if(isPrime(sum - arr[i])==false)
  	                {
  	                    posi = i;
  	                    break;
  	                }
  	            }
  	            for(int i=0;i<n;i++)
  	            {
  	                if(i!=posi)
  	                {
  	                    System.out.print((i+1)+" ");
  	                }
  	            }
  	            System.out.println();
  	        }
  	    }
  	    
  	    
  	}
  	
  	
  	
  	
  	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());
          }
          
          float nextFloat()
          {
              return Float.parseFloat(next());
          }
   
          String nextLine()
          {
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
          
          int[] readArray(int n) {
  			int[] a=new int[n];
  			for (int i=0; i<n; i++) a[i]=nextInt();
  			return a;
  		}
  		
  		long[] readArrayLong(int n) {
  			long[] a=new long[n];
  			for (int i=0; i<n; i++) a[i]=nextLong();
  			return a;
  		}
  		
      }
      
      
      
      public static int[] radixSort2(int[] a)
  	{
  		int n = a.length;
  		int[] c0 = new int[0x101];
  		int[] c1 = new int[0x101];
  		int[] c2 = new int[0x101];
  		int[] c3 = new int[0x101];
  		for(int v : a) {
  			c0[(v&0xff)+1]++;
  			c1[(v>>>8&0xff)+1]++;
  			c2[(v>>>16&0xff)+1]++;
  			c3[(v>>>24^0x80)+1]++;
  		}
  		for(int i = 0;i < 0xff;i++) {
  			c0[i+1] += c0[i];
  			c1[i+1] += c1[i];
  			c2[i+1] += c2[i];
  			c3[i+1] += c3[i];
  		}
  		int[] t = new int[n];
  		for(int v : a)t[c0[v&0xff]++] = v;
  		for(int v : t)a[c1[v>>>8&0xff]++] = v;
  		for(int v : a)t[c2[v>>>16&0xff]++] = v;
  		for(int v : t)a[c3[v>>>24^0x80]++] = v;
  		return a;
  	}
  	
  	static void reverse_sorted(int[] arr)
  	{
  	    ArrayList<Integer> list = new ArrayList<>();
  	    for(int i=0;i<arr.length;i++)
  	    {
  	        list.add(arr[i]);
  	    }
  	    Collections.sort(list , Collections.reverseOrder());
  	    for(int i=0;i<arr.length;i++)
  	    {
  	        arr[i] = list.get(i);
  	    }
  	}
  	
  	static int LowerBound(int a[], int x) { // x is the target value or key
          int l=-1,r=a.length;
          while(l+1<r) {
              int m=(l+r)>>>1;
              if(a[m]>=x) r=m;
              else l=m;
          }
          return r;
      }
      
      static int UpperBound(ArrayList<Integer> list, int x) {// x is the key or target value
          int l=-1,r=list.size();
          while(l+1<r) {
              int m=(l+r)>>>1;
              if(list.get(m)<=x) l=m;
              else r=m;
          }
          return l+1;
      }
      
      public static HashMap<String, Integer> sortByValue(HashMap<String, Integer> hm)
      {
          // Create a list from elements of HashMap
          List<Map.Entry<String, Integer> > list =
                 new LinkedList<Map.Entry<String, Integer> >(hm.entrySet());
   
          // Sort the list
          Collections.sort(list, new Comparator<Map.Entry<String, Integer> >() {
              public int compare(Map.Entry<String, Integer> o1,
                                 Map.Entry<String, Integer> o2)
              {
                  return (o1.getValue()).compareTo(o2.getValue());
              }
          });
           
          // put data from sorted list to hashmap
          HashMap<String, Integer> temp = new LinkedHashMap<String, Integer>();
          for (Map.Entry<String, Integer> aa : list) {
              temp.put(aa.getKey(), aa.getValue());
          }
          return temp;
      }
      
      static class Queue_Pair implements Comparable<Queue_Pair> {
  		int first , second;
  		public Queue_Pair(int first, int second) {
  			this.first=first;
  			this.second=second;
  		}
  		public int compareTo(Queue_Pair o) {
  			return Integer.compare(o.first, first);
  		}
  	}
      
      static void leftRotate(int arr[], int d, int n)
      {
          for (int i = 0; i < d; i++)
              leftRotatebyOne(arr, n);
      }
   
      static void leftRotatebyOne(int arr[], int n)
      {
          int i, temp;
          temp = arr[0];
          for (i = 0; i < n - 1; i++)
              arr[i] = arr[i + 1];
          arr[n-1] = temp;
          
      }
      
      static boolean isPalindrome(String str)
      {
   
          // Pointers pointing to the beginning
          // and the end of the string
          int i = 0, j = str.length() - 1;
   
          // While there are characters to compare
          while (i < j) {
   
              // If there is a mismatch
              if (str.charAt(i) != str.charAt(j))
                  return false;
   
              // Increment first pointer and
              // decrement the other
              i++;
              j--;
          }
   
          // Given string is a palindrome
          return true;
      }
      
      static boolean palindrome_array(char arr[], int n)
      {
          // Initialise flag to zero.
          int flag = 0;
   
          // Loop till array size n/2.
          for (int i = 0; i <= n / 2 && n != 0; i++) {
   
              // Check if first and last element are different
              // Then set flag to 1.
              if (arr[i] != arr[n - i - 1]) {
                  flag = 1;
                  break;
              }
          }
   
          // If flag is set then print Not Palindrome
          // else print Palindrome.
          if (flag == 1)
              return false;
          else
              return true;
      }
      
  	static boolean allElementsEqual(long[] arr,int n)
  	{
  	    int z=0;
  	        for(int i=0;i<n-1;i++)
  		    {
  		        if(arr[i]==arr[i+1])
  		        {
  		            z++;
  		        }
  		    }
  		    if(z==n-1)
  		    {
  		        return true;
  		    }
  		    else
  		    {
  		        return false;
  		    }
  		    
  	}
  	
  	static boolean allElementsDistinct(int[] arr,int n)
  	{
  	    int z=0;
  	        for(int i=0;i<n-1;i++)
  		    {
  		        if(arr[i]!=arr[i+1])
  		        {
  		            z++;
  		        }
  		    }
  		    if(z==n-1)
  		    {
  		        return true;
  		    }
  		    else
  		    {
  		        return false;
  		    }
  		    
  		    
  	}
  	
  	public static void reverse(int[] array)
      {
    
          // Length of the array
          int n = array.length;
    
          // Swaping the first half elements with last half
          // elements
          for (int i = 0; i < n / 2; i++) {
    
              // Storing the first half elements temporarily
              int temp = array[i];
    
              // Assigning the first half to the last half
              array[i] = array[n - i - 1];
    
              // Assigning the last half to the first half
              array[n - i - 1] = temp;
          }
      }
      
      public static void reverse_Long(long[] array)
      {
    
          // Length of the array
          int n = array.length;
    
          // Swaping the first half elements with last half
          // elements
          for (int i = 0; i < n / 2; i++) {
    
              // Storing the first half elements temporarily
              long temp = array[i];
    
              // Assigning the first half to the last half
              array[i] = array[n - i - 1];
    
              // Assigning the last half to the first half
              array[n - i - 1] = temp;
          }
      }
  	
  	static boolean isSorted(int[] a)
      {
          for (int i = 0; i < a.length - 1; i++)
          {
              if (a[i] > a[i + 1]) {
                  return false;
              }
          }
   
          return true;
      }
      
      
      
      static boolean isReverseSorted(int[] a)
      {
          for (int i = 0; i < a.length - 1; i++)
          {
              if (a[i] < a[i + 1]) {
                  return false;
              }
          }
   
          return true;
      }
      
      static int[] rearrangeEvenAndOdd(int arr[], int n)
      {
          ArrayList<Integer> list = new ArrayList<>();
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2==0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2!=0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    int len = list.size();
  		    int[] array = list.stream().mapToInt(i->i).toArray();
  		    return array;
      }
      
      static long[] rearrangeEvenAndOddLong(long arr[], int n)
      {
          ArrayList<Long> list = new ArrayList<>();
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2==0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2!=0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    int len = list.size();
  		    long[] array = list.stream().mapToLong(i->i).toArray();
  		    return array;
      }
  	
  	
      
      static boolean isPrime(long n)
      {
   
          // Check if number is less than
          // equal to 1
          if (n <= 1)
              return false;
   
          // Check if number is 2
          else if (n == 2)
              return true;
   
          // Check if n is a multiple of 2
          else if (n % 2 == 0)
              return false;
   
          // If not, then just check the odds
          for (long i = 3; i <= Math.sqrt(n); i += 2)
          {
              if (n % i == 0)
                  return false;
          }
          return true;
      }
      
      static long getSum(long n)
      {    
          long sum = 0;
            
          while (n != 0)
          {
              sum = sum + n % 10;
              n = n/10;
          }
        
      return sum;
      }
      
      static int gcd(int a, int b)
      {
        if (b == 0)
          return a;
        return gcd(b, a % b);
      }
       
      static long gcdLong(long a, long b)
      {
          if (b == 0)
          return a;
        return gcdLong(b, a % b);
      }
      
      static void swap(int i, int j)
      {
          int temp = i;
          i = j;
          j = temp;
      }
  	
  	static int countDigit(int n)
      {
          return (int)Math.floor(Math.log10(n) + 1);
      }
  	
  }
  
  
  