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

Terms

a(0) =1a(1) =-1a(2) =-1a(3) =29a(4) =275a(5) =1829a(6) =10739a(7) =59429a(8) =318275a(9) =1670789a(10) =8656979a(11) =44454629a(12) =226827875a(13) =1151991749a(14) =5830280819a(15) =29429454629a(16) =148249811075a(17) =745630312709