a(n) = Sum_{k=0..n} binomial(k, 6*(n-k)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =2a(8) =8a(9) =29a(10) =85a(11) =211a(12) =463a(13) =925a(14) =1718a(15) =3017a(16) =5097a(17) =8464a(18) =14197a(19) =24753a(20) =45697a(21) =89150a(22) =180254a(23) =368734a(24) =748924a(25) =1493990a(26) =2914906a(27) =5565127a(28) =10434412a(29) =19322901