a(n) = 5^n + 3^n - 2^n.

Terms

a(0) =1a(1) =6a(2) =30a(3) =144a(4) =690a(5) =3336a(6) =16290a(7) =80184a(8) =396930a(9) =1972296a(10) =9823650a(11) =49003224a(12) =244667970a(13) =1222289256a(14) =6108282210a(15) =30531894264a(16) =152630871810a(17) =763068462216