a(n) = Sum_{k=0..floor(n/10)} binomial(n-5*k,5*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) =7a(12) =22a(13) =57a(14) =127a(15) =253a(16) =463a(17) =793a(18) =1288a(19) =2003a(20) =3005a(21) =4380a(22) =6255a(23) =8855a(24) =12630a(25) =18508a(26) =28358a(27) =45783a(28) =77408a(29) =134883