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 A261798 #44 Mar 19 2019 18:08:39 %S A261798 0,0,0,15,59,0,361,704,1247,0 %N A261798 Maximum water retention of an associative magic square of order n. %C A261798 Two of the most famous magic squares are associative magic squares - the Lo Shu magic square and Dürer's magic square. Al Zimmermann's programming contest in 2010 produced the presently known maximum retention values for magic squares order 4 to 28 A201126. No concerted effort has been made to find the maximum retention for associative magic squares. %C A261798 There are 4211744 different water retention patterns for a 7 x 7 square A054247 and 1.12*10^18 different order 7 associative magic squares. There is no proof that the presently stated maximum retention values greater than order 5 are actually the maximum possible retention. %C A261798 a(11) >= 3226, a(12) >= 4840, a(13) >= 6972. %C A261798 The Wikipedia link below shows the first attempt to classify a set of data by its water retention. Here the 48 associative order 4 magic squares are thus classified. Perhaps there might be some correlation between this surface evaluation and Mohs hardness scale. %H A261798 Craig Knecht, <a href="/A261798/a261798_1.png">Order 5 associative magic square.</a> %H A261798 Craig Knecht, <a href="/A261798/a261798_3.jpg">Order 7 associative magic square.</a> %H A261798 Craig Knecht, <a href="/A261798/a261798_1.jpg">Order 8 associative magic square.</a> %H A261798 Craig Knecht, <a href="/A261798/a261798_4.jpg">Order 9 associative magic square.</a> %H A261798 Craig Knecht, <a href="/A261798/a261798_5.jpg">Order 12 associative magic square.</a> %H A261798 Johan Ofverstedt, <a href="http://uu.diva-portal.org/smash/record.jsf?pid=diva2%3A534020">Water Retention on Magic Squares with Constraint Based Local Search</a>. %H A261798 Wikipedia, <a href="https://commons.wikimedia.org/wiki/Category:Associative_magic_squares_of_order_4">Listing by water retention capacity.</a> and <a href="http://en.wikipedia.org/wiki/Water_retention_on_mathematical_surfaces">Water retention on mathematical surfaces</a>. %e A261798 (16 3 2 13) %e A261798 (5 10 11 8) %e A261798 (9 6 7 12) %e A261798 (4 15 14 1) %e A261798 This is Albrecht Dürer's famous magic square in Melancholia I. Dürer put the date of its creation (1514) in the numbers in the bottom row. This square holds 5 units of water. %Y A261798 Cf. A201126 (water retention on magic squares), A201127 (water retention on semi-magic squares), A261347 (water retention on number squares). %K A261798 nonn,more %O A261798 1,4 %A A261798 _Craig Knecht_, Sep 01 2015