a(n) = Sum_{k=0..n} binomial(k, 9*(n-k)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =1a(10) =2a(11) =11a(12) =56a(13) =221a(14) =716a(15) =2003a(16) =5006a(17) =11441a(18) =24311a(19) =48621a(20) =92380a(21) =167980a(22) =294121a(23) =498751a(24) =824506a(25) =1341154a(26) =2177572a(27) =3605251a(28) =6249101a(29) =11593726