a(n) = 6*n + 1.

Terms

a(0) =1a(1) =7a(2) =13a(3) =19a(4) =25a(5) =31a(6) =37a(7) =43a(8) =49a(9) =55a(10) =61a(11) =67a(12) =73a(13) =79a(14) =85a(15) =91a(16) =97a(17) =103a(18) =109a(19) =115a(20) =121a(21) =127a(22) =133a(23) =139a(24) =145a(25) =151a(26) =157a(27) =163a(28) =169a(29) =175