a(n) = 4*binomial(10*n+8,n)/(5*n+4).

A234571

a(n) = 4*binomial(10*n+8,n)/(5*n+4).

Terms

    a(0) =1a(1) =8a(2) =108a(3) =1776a(4) =32430a(5) =632016a(6) =12876864a(7) =270964320a(8) =5843355957a(9) =128462407840

External references