Fibonacci sequence beginning 3, 12.

Terms

a(0) =3a(1) =12a(2) =15a(3) =27a(4) =42a(5) =69a(6) =111a(7) =180a(8) =291a(9) =471a(10) =762a(11) =1233a(12) =1995a(13) =3228a(14) =5223a(15) =8451a(16) =13674a(17) =22125a(18) =35799a(19) =57924a(20) =93723a(21) =151647a(22) =245370a(23) =397017a(24) =642387a(25) =1039404a(26) =1681791a(27) =2721195a(28) =4402986a(29) =7124181