a(n) = binomial(5*n+3,n)/(n+1).

Terms

a(0) =1a(1) =4a(2) =26a(3) =204a(4) =1771a(5) =16380a(6) =158224a(7) =1577532a(8) =16112057a(9) =167710664a(10) =1772645420a(11) =18974357220a(12) =205263418941