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 A146303 #24 Feb 16 2025 08:33:09 %S A146303 1,4,9,18,58,348,1862,10188,57600,376692,2640422,19469324,151978440, %T A146303 1258451524,10963084588,100087600184 %N A146303 Number of distinct ways to place queens (even fewer than n) on an n X n chessboard so that no queen is attacking another and that it is not possible to add another queen. %C A146303 In other words, number of maximal independent vertex sets (and minimal vertex covers) in the n X n queen graph. - _Eric W. Weisstein_, Jun 20 2017 %H A146303 S. W. Golomb and L. D. Baumert, <a href="http://dx.doi.org/10.1145/321296.321300">Backtrack Programming</a>, Journal of the ACM, 4 (2001), 516-524. %H A146303 Stefan Kral, <a href="/A146303/a146303.cpp.txt">C++11 code using OpenMP</a> %H A146303 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MaximalIndependentVertexSet.html">Maximal Independent Vertex Set</a> %H A146303 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MinimalVertexCover.html">Minimal Vertex Cover</a> %H A146303 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/QueenGraph.html">Queen Graph</a> %e A146303 The a(2) = 4 solutions are to place a single queen in each of the squares of the chessboard. For n=3, there is a single one-queen solution (placing the queen in b2) and eight two-queen solutions, but no three-queen solution (see A000170). %Y A146303 Cf. A000170, A146304. %K A146303 hard,nonn,more %O A146303 1,2 %A A146303 _Paolo Bonzini_, Oct 29 2008 %E A146303 a(12)-a(16) from _Stefan Kral_, Aug 10 2016