a(n) = 2^n + 5^n + 6^n.

Terms

a(0) =3a(1) =13a(2) =65a(3) =349a(4) =1937a(5) =10933a(6) =62345a(7) =358189a(8) =2070497a(9) =12031333a(10) =70232825a(11) =411627229a(12) =2420927057a(13) =14281405333a(14) =84467696105a(15) =500702595469