This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A022681 #13 Sep 08 2022 08:44:46
%S A022681 1,-21,168,-511,-756,8946,-13265,-41604,100023,168819,-192675,
%T A022681 -1687035,551446,9388890,39015,-23757153,-51335655,33287667,289673223,
%U A022681 168014469,-413315910,-2158209675,-1508351355,6477445065
%N A022681 Expansion of Product_{m>=1} (1-m*q^m)^21.
%H A022681 G. C. Greubel, <a href="/A022681/b022681.txt">Table of n, a(n) for n = 0..1000</a>
%p A022681 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
%t A022681 With[{nmax = 50}, CoefficientList[Series[Product[(1 - k*q^k)^21, {k, 1, nmax}], {q, 0, nmax}], q]] (* _G. C. Greubel_, Jul 19 2018 *)
%o A022681 (PARI) m=50; q='q+O('q^m); Vec(prod(n=1,m,(1-n*q^n)^21)) \\ _G. C. Greubel_, Jul 19 2018
%o A022681 (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
%K A022681 sign
%O A022681 0,2
%A A022681 _N. J. A. Sloane_