a(n) = 1^n + 3^n + 4^n.

Terms

a(0) =3a(1) =8a(2) =26a(3) =92a(4) =338a(5) =1268a(6) =4826a(7) =18572a(8) =72098a(9) =281828a(10) =1107626a(11) =4371452a(12) =17308658a(13) =68703188a(14) =273218426a(15) =1088090732a(16) =4338014018a(17) =17309009348a(18) =69106897226a(19) =276040168412