fastfunc isprim num .
   i = 2
   while i <= sqrt num
      if num mod i = 0
         return 0
      .
      i += 1
   .
   return 1
.
n = 2
repeat
   if isprim n = 1 and isprim (2 * n + 1) = 1
      write n & " "
      cnt += 1
   .
   until cnt = 50
   n += 1
.
