A022680 Expansion of Product_{m>=1} (1-m*q^m)^20.

1, -20, 150, -400, -875, 7396, -7770, -36600, 56510, 154660, -872, -1314200, -455605, 6284960, 3781830, -9954864, -43558410, -16664680, 165132890, 229738040, 57372644, -1326447180, -2095012310, 1723402120, 7805180205

Offset: 0

Author

N. J. A. Sloane

Keywords

• sign

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000

Programs

Magma

Coefficients(&*[(1-m*x^m)^20:m in [1..40]])[1..40] where x is PolynomialRing(Integers()).1; // G. C. Greubel, Jul 18 2018

Mathematica

With[{nmax = 50}, CoefficientList[Series[Product[(1 - k*q^k)^20, {k, 1, nmax}], {q, 0, nmax}], q]] (* G. C. Greubel, Jul 18 2018 *)

PARI

m=50; q='q+O('q^m); Vec(prod(n=1,m,(1-n*q^n)^20)) \\ G. C. Greubel, Jul 18 2018