Numbers that are divisible only by primes congruent to 1 mod 4.

Terms

a(0) =1a(1) =5a(2) =13a(3) =17a(4) =25a(5) =29a(6) =37a(7) =41a(8) =53a(9) =61a(10) =65a(11) =73a(12) =85a(13) =89a(14) =97a(15) =101a(16) =109a(17) =113a(18) =125a(19) =137a(20) =145a(21) =149a(22) =157a(23) =169a(24) =173a(25) =181a(26) =185a(27) =193a(28) =197a(29) =205