Powers of sqrt(13) rounded down.

Terms

a(0) =1a(1) =3a(2) =13a(3) =46a(4) =169a(5) =609a(6) =2197a(7) =7921a(8) =28561a(9) =102978a(10) =371293a(11) =1338715a(12) =4826809a(13) =17403307a(14) =62748517a(15) =226242995a(16) =815730721a(17) =2941158941a(18) =10604499373a(19) =38235066239a(20) =137858491849a(21) =497055861119