a(n) = 1 - n^4.

Terms

a(0) =1a(1) =0a(2) =-15a(3) =-80a(4) =-255a(5) =-624a(6) =-1295a(7) =-2400a(8) =-4095a(9) =-6560a(10) =-9999a(11) =-14640a(12) =-20735a(13) =-28560a(14) =-38415a(15) =-50624a(16) =-65535a(17) =-83520a(18) =-104975a(19) =-130320a(20) =-159999a(21) =-194480a(22) =-234255a(23) =-279840a(24) =-331775a(25) =-390624a(26) =-456975a(27) =-531440a(28) =-614655a(29) =-707280