a(n) = 153*n + 18.

Terms

a(0) =18a(1) =171a(2) =324a(3) =477a(4) =630a(5) =783a(6) =936a(7) =1089a(8) =1242a(9) =1395a(10) =1548a(11) =1701a(12) =1854a(13) =2007a(14) =2160a(15) =2313a(16) =2466a(17) =2619a(18) =2772a(19) =2925a(20) =3078a(21) =3231a(22) =3384a(23) =3537a(24) =3690a(25) =3843a(26) =3996a(27) =4149a(28) =4302a(29) =4455