Fibonacci sequence beginning 3, 15.

Terms

a(0) =3a(1) =15a(2) =18a(3) =33a(4) =51a(5) =84a(6) =135a(7) =219a(8) =354a(9) =573a(10) =927a(11) =1500a(12) =2427a(13) =3927a(14) =6354a(15) =10281a(16) =16635a(17) =26916a(18) =43551a(19) =70467a(20) =114018a(21) =184485a(22) =298503a(23) =482988a(24) =781491a(25) =1264479a(26) =2045970a(27) =3310449a(28) =5356419a(29) =8666868