a(n) = 7*binomial(5*n+7, n)/(5*n+7).

Terms

a(0) =1a(1) =7a(2) =56a(3) =490a(4) =4550a(5) =44051a(6) =439824a(7) =4496388a(8) =46834095a(9) =495260150a(10) =5303177880a(11) =57385471962a(12) =626548297648