a(n) = Lucas(n+4) - 2*(n+3).

Terms

a(0) =1a(1) =3a(2) =8a(3) =17a(4) =33a(5) =60a(6) =105a(7) =179a(8) =300a(9) =497a(10) =817a(11) =1336a(12) =2177a(13) =3539a(14) =5744a(15) =9313a(16) =15089a(17) =24436a(18) =39561a(19) =64035a(20) =103636a(21) =167713a(22) =271393a(23) =439152a(24) =710593a(25) =1149795a(26) =1860440a(27) =3010289a(28) =4870785a(29) =7881132