a(n) = (4*7^n + (-3)^n)/5.

Terms

a(0) =1a(1) =5a(2) =41a(3) =269a(4) =1937a(5) =13397a(6) =94265a(7) =658397a(8) =4613153a(9) =32278949a(10) =225992009a(11) =1581825965a(12) =11073136049a(13) =77510889461a(14) =542579414873