a(n) = 5^n - 4^n - 3^n - 2^n.

Terms

a(0) =-2a(1) =-4a(2) =-4a(3) =26a(4) =272a(5) =1826a(6) =10736a(7) =59426a(8) =318272a(9) =1670786a(10) =8656976a(11) =44454626a(12) =226827872a(13) =1151991746a(14) =5830280816a(15) =29429454626a(16) =148249811072a(17) =745630312706