a(n) = 6*n+3.

Terms

a(0) =3a(1) =9a(2) =15a(3) =21a(4) =27a(5) =33a(6) =39a(7) =45a(8) =51a(9) =57a(10) =63a(11) =69a(12) =75a(13) =81a(14) =87a(15) =93a(16) =99a(17) =105a(18) =111a(19) =117a(20) =123a(21) =129a(22) =135a(23) =141a(24) =147a(25) =153a(26) =159a(27) =165a(28) =171a(29) =177