A022681 Expansion of Product_{m>=1} (1-m*q^m)^21.

1, -21, 168, -511, -756, 8946, -13265, -41604, 100023, 168819, -192675, -1687035, 551446, 9388890, 39015, -23757153, -51335655, 33287667, 289673223, 168014469, -413315910, -2158209675, -1508351355, 6477445065

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)^21:m in [1..40]])[1..40] where x is PolynomialRing(Integers()).1; // G. C. Greubel, Jul 19 2018

Maple

seq(coeff(series(mul((1-m*x^m)^21,m=1..n), x,n+1),x,n),n=0..30); # Muniru A Asiru, Jul 19 2018

Mathematica

With[{nmax = 50}, CoefficientList[Series[Product[(1 - k*q^k)^21, {k, 1, nmax}], {q, 0, nmax}], q]] (* G. C. Greubel, Jul 19 2018 *)

PARI

m=50; q='q+O('q^m); Vec(prod(n=1,m,(1-n*q^n)^21)) \\ G. C. Greubel, Jul 19 2018