a(n) = ((7+sqrt(3))^n + (7-sqrt(3))^n) / 2.

Terms

a(0) =1a(1) =7a(2) =52a(3) =406a(4) =3292a(5) =27412a(6) =232336a(7) =1991752a(8) =17197072a(9) =149138416a(10) =1296872512a(11) =11295848032a(12) =98485736896a(13) =859191307072