G.f.: A(x) = Product_{n>=1} [ (1-x)^3*(1 + 3x + 6x^2 +...+ n(n+1)/2*x^(n-1)) ].

Terms

a(0) =1a(1) =-3a(2) =-3a(3) =15a(4) =-15a(5) =66a(6) =-261a(7) =618a(8) =-1155a(9) =1040a(10) =2361a(11) =-11616a(12) =23733a(13) =-27027a(14) =29394a(15) =-132318a(16) =545790a(17) =-1383459a(18) =2418896a(19) =-3383679a(20) =4278462a(21) =-3127320a(22) =-8332866a(23) =42021990a(24) =-99069516a(25) =160683318a(26) =-200247795a(27) =214883010a(28) =-345461022a(29) =1184850729