a(n) = 11^n - 3^n.

Terms

a(0) =0a(1) =8a(2) =112a(3) =1304a(4) =14560a(5) =160808a(6) =1770832a(7) =19484984a(8) =214352320a(9) =2357928008a(10) =25937365552a(11) =285311493464