a(n) = Sum_{k=0..floor(2*n/5)} binomial(2*k,2*n-5*k).

Terms

a(0) =1a(1) =0a(2) =0a(3) =2a(4) =0a(5) =1a(6) =6a(7) =1a(8) =6a(9) =20a(10) =7a(11) =28a(12) =70a(13) =38a(14) =121a(15) =253a(16) =186a(17) =505a(18) =938a(19) =859a(20) =2069a(21) =3553a(22) =3822a(23) =8390a(24) =13700a(25) =16577a(26) =33834a(27) =53585a(28) =70607a(29) =136078