a(n) = 9*binomial(7*n+9, n)/(7*n+9).

A233907

a(n) = 9*binomial(7*n+9, n)/(7*n+9).

Terms

    a(0) =1a(1) =9a(2) =99a(3) =1218a(4) =16065a(5) =222138a(6) =3178140a(7) =46656324a(8) =698868216a(9) =10639125640a(10) =164128169205

External references