a(n) = 5*6^n - 4*5^n.

Terms

a(0) =1a(1) =10a(2) =80a(3) =580a(4) =3980a(5) =26380a(6) =170780a(7) =1087180a(8) =6835580a(9) =42575980a(10) =263268380a(11) =1618672780a(12) =9907349180a(13) =60420657580a(14) =367406757980