a(n) = 2^n + 3^n + 4^n.

Terms

a(0) =3a(1) =9a(2) =29a(3) =99a(4) =353a(5) =1299a(6) =4889a(7) =18699a(8) =72353a(9) =282339a(10) =1108649a(11) =4373499a(12) =17312753a(13) =68711379a(14) =273234809a(15) =1088123499a(16) =4338079553a(17) =17309140419a(18) =69107159369a(19) =276040692699