a(n) = n*(n-1)*7^n.

Terms

a(0) =0a(1) =98a(2) =2058a(3) =28812a(4) =336140a(5) =3529470a(6) =34588806a(7) =322828856a(8) =2905459704a(9) =25422772410a(10) =217505941730