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 A260189 #11 Jul 22 2015 23:07:59 %S A260189 1,0,0,1,1,0,0,0,0,0,0,1,1,0,0,4,8,0,0,15,22,0,0,52,51,0,0,257,342,0, %T A260189 0,1589,2609,0,0,11417,16896,0,0,75375,99114,0,0,616010,876579,0,0, %U A260189 5253278,8551800,0,0,49667373,79595269,0,0,525731268,764804085,0,0,5932910966,8905825760,0,0 %N A260189 a(n) = A033148(n) / 2^floor(n/4). %D A260189 W. Ahrens, Mathematische Unterhaltungen und Spiele, 2nd edition, volume 1, Teubner, 1910, pages 249-258. %D A260189 Maurice Kraitchik, Le probleme des reines, Bruxelles: L'Échiquier, 1926, 18. %H A260189 P. Capstick and K. McCann, <a href="/A000170/a000170_1.pdf">The problem of the n queens</a>, apparently unpublished, no date (circa 1990?) [Scanned copy] %Y A260189 Cf. A002562, A032522, A033148, A037223, A037224. %K A260189 nonn,hard %O A260189 1,16 %A A260189 _Vaclav Kotesovec_, following a suggestion of _Don Knuth_, Jul 18 2015