Primes p such that 21 is not a square mod p.

Terms

a(0) =2a(1) =11a(2) =13a(3) =19a(4) =23a(5) =29a(6) =31a(7) =53a(8) =61a(9) =71a(10) =73a(11) =97a(12) =103a(13) =107a(14) =113a(15) =137a(16) =139a(17) =149a(18) =157a(19) =179a(20) =181a(21) =191a(22) =197a(23) =199a(24) =223a(25) =229a(26) =233a(27) =239a(28) =241a(29) =263