a(n) = 5^n - 3^n - 2^n.

Terms

a(0) =0a(1) =12a(2) =90a(3) =528a(4) =2850a(5) =14832a(6) =75810a(7) =383808a(8) =1932930a(9) =9705552a(10) =48648930a(11) =243605088a(12) =1219100610a(13) =6098716272a(14) =30503196450a(15) =152544778368a(16) =762810181890