a(n) = 3*n + 1.

Terms

a(0) =1a(1) =4a(2) =7a(3) =10a(4) =13a(5) =16a(6) =19a(7) =22a(8) =25a(9) =28a(10) =31a(11) =34a(12) =37a(13) =40a(14) =43a(15) =46a(16) =49a(17) =52a(18) =55a(19) =58a(20) =61a(21) =64a(22) =67a(23) =70a(24) =73a(25) =76a(26) =79a(27) =82a(28) =85a(29) =88