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: """
  // Author : snape_here - Susanta Mukherjee
       
   """
  
  from __future__ import division, print_function
   
  import os,sys
  from io import BytesIO, IOBase
   
  if sys.version_info[0] < 3:
      from __builtin__ import xrange as range
      from future_builtins import ascii, filter, hex, map, oct, zip
   
  def ii(): return int(input())
  def fi(): return float(input())
  def si(): return input()
  def msi(): return map(str,input().split())
  def mi(): return map(int,input().split())
  def li(): return list(mi())
  def lsi(): return list(msi())
   
  def read():
      sys.stdin = open('input.txt', 'r')  
      sys.stdout = open('output.txt', 'w') 
  
  def isPrime(n) :
      if (n <= 1) : return False
      if (n <= 3) : return True
      if (n % 2 == 0 or n % 3 == 0) : return False
      i = 5
      while(i * i <= n) : 
          if (n % i == 0 or n % (i + 2) == 0) : 
              return False
          i = i + 6
      return True
   
  def gcd(x, y):
      while y:
          x, y = y, x % y
      return x
  
  def lcm(x, y):
      return (x*y)//(gcd(x,y))
  
  mod=1000000007
  
  def modInverse(b,m): 
      g = gcd(b, m)  
      if (g != 1):         
          return -1
      else:          
          return pow(b, m - 2, m) 
  
  def ceil2(x,y):
      if x%y==0:
          return x//y
      else:
          return x//y+1
  
  def modu(a,b,m): 
  
      a = a % m 
      inv = modInverse(b,m) 
      if(inv == -1): 
          return -999999999
      else: 
          return (inv*a)%m
  
  from math import log,factorial,cos,tan,sin,radians,floor,sqrt,ceil,log2
  
  import bisect
  import random
  import string 
  
  from decimal import *
  
  getcontext().prec = 50
  
  abc="abcdefghijklmnopqrstuvwxyz"
  
  pi=3.141592653589793238
  
  def gcd1(a):
      if len(a) == 1:
          return a[0]
      ans = a[0]
      for i in range(1,len(a)):
          ans = gcd(ans,a[i])
      return ans
  
  def mykey(x):
      return len(x)
  
  def main():
  
      for _ in range(ii()):
          n=ii()
          a=li()
          s=sum(a)
          if not isPrime(s):
              print(n)
              ans = []
              for i in range(1,n+1):
                  ans.append(i)
              print(*ans)
          else:
              print(n-1)
              pos = -1
              ans = []
              for i in range(n):
                  if pos==-1 and a[i]%2:
                      pos = i
                  else:
                      ans.append(i+1)
              print(*ans)
  
  
          # print("Case #",end="")
          # print(_+1,end="")
          # print(": ",end="")
          # print(ans)
  
  
  # region fastio
  
  # template taken from https://github.com/cheran-senthil/PyRival/blob/master/templates/template.py
  
  BUFSIZE = 8192
   
  
  class FastIO(IOBase):
      newlines = 0
   
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
   
      def read(self):
          while True:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
   
      def readline(self):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
   
      def flush(self):
          if self.writable:
              os.write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
   
   
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
   
   
  def print(*args, **kwargs):
      """Prints the values to a stream, or to sys.stdout by default."""
      sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
      at_start = True
      for x in args:
          if not at_start:
              file.write(sep)
          file.write(str(x))
          at_start = False
      file.write(kwargs.pop("end", "\n"))
      if kwargs.pop("flush", False):
          file.flush()
   
   
  if sys.version_info[0] < 3:
      sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
  else:
      sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
   
  input = lambda: sys.stdin.readline().rstrip("\r\n")
   
  # endregion
  
   
  if __name__ == "__main__":
      #read()
      main()