Divisible only by primes congruent to 1 mod 3.

Terms

a(0) =1a(1) =7a(2) =13a(3) =19a(4) =31a(5) =37a(6) =43a(7) =49a(8) =61a(9) =67a(10) =73a(11) =79a(12) =91a(13) =97a(14) =103a(15) =109a(16) =127a(17) =133a(18) =139a(19) =151a(20) =157a(21) =163a(22) =169a(23) =181a(24) =193a(25) =199a(26) =211a(27) =217a(28) =223a(29) =229