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 A271802 #10 Sep 15 2019 04:07:17
%S A271802 0,6,52,614,16000,1114394,220762028,127074234622,215163221802400,
%T A271802 1080509693050320314,16181730102294154610684,
%U A271802 725449589191165593072311582,97631783799192329642727718567824,39528641527526180063041016094650084850
%N A271802 Number of cuttings of an n X n checkerboard along grid lines into two pieces with holes disallowed.
%C A271802 Equivalently, the number of partitionings of an n X n checkerboard into two edgewise-connected simply-connected sets. (Cf. A068416).
%C A271802 Each part is required to contain at least one cell and cuttings are considered different if they only differ by rotation or reflection.
%F A271802 a(n) = A068416(n) - A140517(n-2).
%t A271802 A068416 = Cases[Import["https://oeis.org/A068416/b068416.txt", "Table"], {_, _}][[All, 2]];
%t A271802 A140517 = Cases[Import["https://oeis.org/A140517/b140517.txt", "Table"], {_, _}][[All, 2]];
%t A271802 a[n_] := If[n == 1, 0, A068416[[n]] - A140517[[n - 1]]];
%t A271802 Array[a, 14] (* _Jean-François Alcover_, Sep 15 2019 *)
%K A271802 nonn
%O A271802 1,2
%A A271802 _Andrew Howroyd_, Apr 14 2016