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 A291187 #26 Jul 02 2018 20:28:26 %S A291187 288,28200960,29136487207403520,1903816047972624930994913280000 %N A291187 Number of 2 X n Sudoku grids ((2*n) X (2*n) grids divided into 2 X n boxes). %H A291187 Kjell Fredrik Pettersen (after work by Ed Russell), <a href="http://www.afjarvis.staff.shef.ac.uk/sudoku/sud25gp.html">There are 4743933602050718 essentially different Sudoku 2x5 grids</a>. In A. F. Jarvis, <a href="http://www.afjarvis.staff.shef.ac.uk/sudoku/">Sudoku enumeration problems</a>, 2008. %H A291187 Ed Russell, <a href="http://www.afjarvis.staff.shef.ac.uk/sudoku/sud24gp.html">There are 1673187 essentially different Sudoku 2x4 grids</a>. In A. F. Jarvis, <a href="http://www.afjarvis.staff.shef.ac.uk/sudoku/">Sudoku enumeration problems</a>, 2008. %H A291187 Ed Russell and Frazer Jarvis, <a href="http://www.afjarvis.staff.shef.ac.uk/sudoku/sud23gp.html">There are 49 essentially different Sudoku 2x3 grids</a>, 2008. %H A291187 Jordy Vanpoucke, <a href="http://homepages.vub.ac.be/~jvpoucke/MasterThesisMOLS.pdf">Mutually orthogonal latin squares and their generalizations</a> %H A291187 Wikipedia, <a href="https://en.wikipedia.org/wiki/Mathematics_of_Sudoku">Mathematics of Sudoku</a> %Y A291187 Cf. A107739, A291188. %K A291187 nonn,more %O A291187 2,1 %A A291187 _Seiichi Manyama_, Aug 19 2017