a(n) = (6^n/n!)*Product_{k=0..n-1} (6*k + 1).

A004993

a(n) = (6^n/n!)*Product_{k=0..n-1} (6*k + 1).

Terms

    a(0) =1a(1) =6a(2) =126a(3) =3276a(4) =93366a(5) =2800980a(6) =86830380a(7) =2753763480a(8) =88808872230

External references