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

Terms

a(0) =1a(1) =1a(2) =1a(3) =7a(4) =57a(5) =254a(6) =859a(7) =3004a(8) =12393a(9) =53143a(10) =215766a(11) =843756a(12) =3321891a(13) =13333932a(14) =53774932a(15) =215492564a(16) =859595529a(17) =3431847189a(18) =13733091643a(19) =54986385093a(20) =219993856006a(21) =879683351911