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

Terms

a(0) =2a(1) =14a(2) =106a(3) =854a(4) =7186a(5) =62174a(6) =547066a(7) =4861094a(8) =43437346a(9) =389373614a(10) =3496550026a(11) =31429887734a(12) =282673677106