a(n) = 3^n + 4^n + 6^n.

Terms

a(0) =3a(1) =13a(2) =61a(3) =307a(4) =1633a(5) =9043a(6) =51481a(7) =298507a(8) =1751713a(9) =10359523a(10) =61573801a(11) =367168507a(12) =2194090993a(13) =13129397203a(14) =78637382521a(15) =471273075307