a(n) = 9^n+6^n-1^n.

Terms

a(0) =1a(1) =14a(2) =116a(3) =944a(4) =7856a(5) =66824a(6) =578096a(7) =5062904a(8) =44726336a(9) =397498184a(10) =3547250576a(11) =31743856664a(12) =284606318816