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

Terms

a(0) =1a(1) =4a(2) =20a(3) =106a(4) =560a(5) =2914a(6) =14960a(7) =76066a(8) =384320a(9) =1933954a(10) =9707600a(11) =48653026a(12) =243613280a(13) =1219116994a(14) =6098749040a(15) =30503261986a(16) =152544909440a(17) =762810444034