a(n) = (9^n - 8^n - 7^n - 6^n + 4*5^n)/2.

Terms

a(0) =1a(1) =4a(2) =16a(3) =79a(4) =634a(5) =7099a(6) =83746a(7) =947419a(8) =10193794a(9) =105291979a(10) =1054581826a(11) =10323156859a(12) =99334276354a(13) =943521561259