Expansion of Product_{k>=1} ((1 - x^k)/(1 + x^k))^(sigma_2(k)).

Terms

a(0) =1a(1) =-2a(2) =-8a(3) =-2a(4) =30a(5) =110a(6) =92a(7) =-182a(8) =-976a(9) =-2064a(10) =-1488a(11) =3714a(12) =17618a(13) =35814a(14) =37680a(15) =-25278a(16) =-216910a(17) =-541538a(18) =-819268a(19) =-480334a(20) =1441634a(21) =5924858a(22) =12518720a(23) =16883366a(24) =7972200a(25) =-32275008a(26) =-120780700a(27) =-250726492a(28) =-349220282a(29) =-229745138