a(n) = 3^n + 8^n + 9^n.

Terms

a(0) =3a(1) =20a(2) =154a(3) =1268a(4) =10738a(5) =92060a(6) =794314a(7) =6882308a(8) =59830498a(9) =521657900a(10) =4560585274a(11) =39971171348a(12) =351149544658