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 A232820 #15 Nov 14 2014 13:20:50
%S A232820 1,18,144,0,-28200,-814968,-15203328,0,16696909080,893794451000,
%T A232820 25789252433472,0,-54804262577596532,-4044941639317807200,
%U A232820 -161017938434267136000,0,621130358284578576358416,59512584052525004199214632,3008072527724272784969384000,0
%N A232820 Imaginary part of the sum over the n-th powers of all Gaussian integers in the n X n base square in the first quadrant.
%H A232820 Colin Barker, <a href="/A232820/b232820.txt">Table of n, a(n) for n = 1..200</a>
%F A232820 Conjecture: a(4n) = 0. - _Michel Marcus_, Nov 09 2014
%t A232820 g[n_] := Sum[(a + b I)^n, {a, 1, n}, {b, 1, n}]; Table[Im[g[n]], {n, 33}]
%o A232820 (PARI) vector(100, n, imag(sum(x=1, n, sum(y=1, n, (x+I*y)^n)))) \\ _Colin Barker_, Nov 09 2014
%Y A232820 Cf. A230308-A230310, A073763, A232819.
%K A232820 sign
%O A232820 1,2
%A A232820 _José María Grau Ribas_, Nov 30 2013