a(n) = Sum_{k=0..floor(n/9)} (-1)^k*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) =0a(10) =-9a(11) =-54a(12) =-219a(13) =-714a(14) =-2001a(15) =-5004a(16) =-11439a(17) =-24309a(18) =-48618a(19) =-92358a(20) =-167769a(21) =-292599a(22) =-490104a(23) =-783540a(24) =-1172907a(25) =-1562274a(26) =-1562274a(27) =0a(28) =6216183a(29) =24581880