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 A264667 #27 Jun 23 2018 02:36:17 %S A264667 2,4,28,108,2,13968,480,7914054,433284,18726123500,256, %T A264667 178290006448984,14454384,6631290958957860856,1401615406696, %U A264667 941558205279187913101914,1767136,500995759754153499284692617816,31163356068736,984452644453618816989710782436259368 %N A264667 Number of optimal solutions to the maximal number of diagonals problem studied in A264041. %C A264667 Solutions that differ by a rotation and/or reflection are counted as different. - _N. J. A. Sloane_, Nov 20 2015 %C A264667 The paper by Boyland et al. gives a(13) = 14454384 and a(15) = 1401615406696. - _Eric M. Schmidt_, Aug 30 2017 %H A264667 Peter Boyland, Gabriella Pintér, István Laukó, Ivan Roth, Jon E. Schoenfield, and Stephen Wasielewski, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL20/Pinter/pinter3.html">On the Maximum Number of Non-intersecting Diagonals in an Array</a>, Journal of Integer Sequences, Vol. 20 (2017), Article 17.2.4. %e A264667 For n=2 the 4 solutions are: %e A264667 .\ %e A264667 \\ %e A264667 -- %e A264667 /. %e A264667 // %e A264667 -- %e A264667 \\ %e A264667 \. %e A264667 -- %e A264667 // %e A264667 ./ %e A264667 -- %e A264667 where the dot indicates an empty cell. %Y A264667 Cf. A264041. %K A264667 nonn %O A264667 1,1 %A A264667 _Rob Pratt_, Nov 20 2015 %E A264667 a(8)-a(13) from _Andrew Howroyd_, Feb 03 2018 %E A264667 a(14)-a(20) from _Andrew Howroyd_, Jun 22 2018