a(n) = 5^n + 4^n - 3^n.

Terms

a(0) =1a(1) =6a(2) =32a(3) =162a(4) =800a(5) =3906a(6) =18992a(7) =92322a(8) =449600a(9) =2195586a(10) =10755152a(11) =52845282a(12) =260386400a(13) =1286217666a(14) =6367168112a(15) =31576971042a(16) =156839811200a(17) =779990182146