a(n) = a(n-1) - (n-1)*a(n-4), with a(0) = 0, a(1) = 1, a(2) = 2, a(3) = 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =1a(4) =1a(5) =-3a(6) =-13a(7) =-19a(8) =-26a(9) =-2a(10) =115a(11) =305a(12) =591a(13) =615a(14) =-880a(15) =-5150a(16) =-14015a(17) =-23855a(18) =-8895a(19) =83805a(20) =350090a(21) =827190a(22) =1013985a(23) =-829725a(24) =-8881795a(25) =-28734355a(26) =-54083980a(27) =-32511130a(28) =207297335a(29) =1011859275