Expansion of Product_{k>=1} (1 - x^k)^21.

Terms

a(0) =1a(1) =-21a(2) =189a(3) =-910a(4) =2205a(5) =-378a(6) =-13321a(7) =33345a(8) =-10395a(9) =-86870a(10) =122703a(11) =46683a(12) =-98287a(13) =-264915a(14) =96390a(15) =1163064a(16) =-1113588a(17) =-1066527a(18) =1042055a(19) =536025a(20) =2287467a(21) =-3603805a(22) =-1391733a(23) =478170a(24) =-562555a(25) =13742379a(26) =-7889805