a(n) = 5^n + 6^n.

Terms

a(0) =2a(1) =11a(2) =61a(3) =341a(4) =1921a(5) =10901a(6) =62281a(7) =358061a(8) =2070241a(9) =12030821a(10) =70231801a(11) =411625181a(12) =2420922961a(13) =14281397141a(14) =84467679721a(15) =500702562701