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

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =2a(10) =11a(11) =56a(12) =221a(13) =716a(14) =2003a(15) =5006a(16) =11441a(17) =24311a(18) =48622a(19) =92398a(20) =168151a(21) =295261a(22) =504736a(23) =850840a(24) =1442101a(25) =2523676a(26) =4686826a(27) =9373652a(28) =20030039a(29) =44612702