Coefficient of y^0 in G(x,y)^4 where G(x,y) = Sum_{n=-oo..+oo} (1-x^n)^n * x^n * y^n.

Terms

a(0) =1a(1) =-12a(2) =18a(3) =20a(4) =24a(5) =-96a(6) =-4a(7) =-120a(8) =138a(9) =-116a(10) =456a(11) =-132a(12) =356a(13) =-540a(14) =900a(15) =-1884a(16) =1440a(17) =-2076a(18) =1546a(19) =-3204a(20) =5772a(21) =-6572a(22) =7860a(23) =-7440a(24) =12240a(25) =-13128a(26) =15828a(27) =-18632a(28) =23916a(29) =-31344