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 A362291 #21 Apr 25 2023 09:42:15 %S A362291 1,2,68,26098,1408886,12369296230,673890139470,33193434883028584 %N A362291 Number of pairs of disjoint subsets of 1..n^2 of size 2*floor(n/2) having equal sum. %F A362291 a(n) = A362280(n)/((m!)^2 * (n^2-2m)!), where m = 2*floor(n/2). %o A362291 (Python) %o A362291 from math import factorial %o A362291 from itertools import combinations as C %o A362291 def a(n): %o A362291 E = [i for i in range(1, n**2+1)] %o A362291 m = n if n%2 == 0 else n-1 %o A362291 return sum(1 for u in C(E, 2*m) for t in C(u, m) if 2*sum(t)==sum(u)) %o A362291 print([a(n) for n in range(1, 5)]) %Y A362291 Cf. A052928, A362280. %K A362291 nonn,hard,more %O A362291 1,2 %A A362291 _Michael S. Branicky_, Apr 14 2023 %E A362291 a(6)-a(7) from _Martin Ehrenstein_, Apr 16 2023 %E A362291 a(8) from _Martin Ehrenstein_, Apr 25 2023