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 A120282 #5 Aug 05 2025 22:55:25
%S A120282 -1,1,-5,7,-15,7601,-91,3617,-745739,3317609,-5981591,5436374093,
%T A120282 -213827575,213745149261,-249859397004145,238988952277727,
%U A120282 -28354566442037,26315271553053477373,-108409774812137683,3394075340453838586663
%N A120282 Numerator of the coefficients of k^2 term at Sum[Sum[(i-j)^(2n),{i,1,k}],{j,1,k}].
%F A120282 a(n) = numerator[Coefficient[Sum[Sum[(i-j)^(2n),{i,1,k}],{j,1,k}],k,2]]. a(n) = A027643(2n+3) - bisection of numerators of poly-Bernoulli numbers B_n^(k) with k=2.
%t A120282 Numerator[Coefficient[Table[Sum[Sum[(i-j)^(2n),{i,1,k}],{j,1,k}],{n,1,20}],k,2]]
%Y A120282 Cf. A027643.
%K A120282 frac,sign
%O A120282 1,3
%A A120282 _Alexander Adamchuk_, Jul 06 2006