a(n) = 3^n + 4^n + 9^n.

Terms

a(0) =3a(1) =16a(2) =106a(3) =820a(4) =6898a(5) =60316a(6) =536266a(7) =4801540a(8) =43118818a(9) =387702316a(10) =3487892026a(11) =31385431060a(12) =282446845138