11^n-8^n+1.

Terms

a(0) =1a(1) =4a(2) =58a(3) =820a(4) =10546a(5) =128284a(6) =1509418a(7) =17390020a(8) =197581666a(9) =2223729964a(10) =24863682778a(11) =276721736020