a(n) = 2^n + 5^n + 9^n.

Terms

a(0) =3a(1) =16a(2) =110a(3) =862a(4) =7202a(5) =62206a(6) =547130a(7) =4861222a(8) =43437602a(9) =389374126a(10) =3496551050a(11) =31429889782a(12) =282673681202