a(n) = Product_{k = 1..n-1} (9*k - 3).

A147630

a(n) = Product_{k = 1..n-1} (9*k - 3).

Terms

    a(0) =1a(1) =6a(2) =90a(3) =2160a(4) =71280a(5) =2993760a(6) =152681760a(7) =9160905600a(8) =632102486400

External references