Squares that become a prime number when prefixed with a 2.

Terms

a(0) =9a(1) =81a(2) =441a(3) =729a(4) =1089a(5) =1521a(6) =6561a(7) =8649a(8) =16641a(9) =19881a(10) =33489a(11) =53361a(12) =56169a(13) =71289a(14) =74529a(15) =84681a(16) =88209a(17) =103041a(18) =168921a(19) =173889a(20) =251001a(21) =257049a(22) =263169a(23) =269361a(24) =288369a(25) =301401a(26) =314721a(27) =335241a(28) =370881a(29) =423801