a(n) = 5^n - 4^n - 3^n.

Terms

a(0) =-1a(1) =-2a(2) =0a(3) =34a(4) =288a(5) =1858a(6) =10800a(7) =59554a(8) =318528a(9) =1671298a(10) =8658000a(11) =44456674a(12) =226831968a(13) =1151999938a(14) =5830297200a(15) =29429487394a(16) =148249876608a(17) =745630443778