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 A212271 #19 May 17 2021 15:51:38 %S A212271 2,9,80,1600,79033,8156736,2055960192,1108756350625,1411080429618656, %T A212271 3943472747846953216,25425527581172360096017, %U A212271 365481944233773616212640000,11980566143208960475692367828480,882106482533191605447029340350009049,147314997388032765439791110273770608260928 %N A212271 Number of ways to place k non-attacking ferses on an n x n cylindrical chessboard, summed over all k >= 0. %C A212271 Fers is a leaper [1,1]. %H A212271 Vaclav Kotesovec, <a href="/A212271/b212271.txt">Table of n, a(n) for n = 1..18</a> %H A212271 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013, p.443 %F A212271 Limit n ->infinity (a(n))^(1/n^2) is the hard square entropy constant A085850. %Y A212271 Cf. A067965, A067960, A182407, A212269, A212270. %K A212271 nonn,hard %O A212271 1,1 %A A212271 _Vaclav Kotesovec_, May 12 2012