Divisible only by primes congruent to 1 mod 5.

Terms

a(0) =1a(1) =11a(2) =31a(3) =41a(4) =61a(5) =71a(6) =101a(7) =121a(8) =131a(9) =151a(10) =181a(11) =191a(12) =211a(13) =241a(14) =251a(15) =271a(16) =281a(17) =311a(18) =331a(19) =341a(20) =401a(21) =421a(22) =431a(23) =451a(24) =461a(25) =491a(26) =521a(27) =541a(28) =571a(29) =601