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 A062164 #7 Feb 15 2025 14:52:31
%S A062164 1,0,0,1,1,1,3,6,20,40,191,953,4604,24660,158466,1009395
%N A062164 Number of ways of placing n nonattacking (normal) queens on n X n board; solutions congruent on the torus count only once.
%C A062164 In this sequence two n-queens solutions p and q are considered equivalent iff there are natural numbers x and y such that, for all k from {0, ..., n-1}, q (k + x mod n) = p (k) + y mod n, or q is a rotation or a reflection of such a q.
%C A062164 In other words, besides rotations and reflections, also torus shifts are allowed. The sequence reduces the objects of A002562 and via that of A000170. The reduction of A000170 to this sequence is exactly the same as from A007705 to A053994 for torus queens; however, a solution for torus queens remains always a solution after a shift while a normal queens solutions does so only sometimes.
%C A062164 Note that the equivalence classes of this sequence are a subset of A006841. Moreover they are a subset of A062167.
%H A062164 M. Engelhardt, <a href="http://www.nqueens.de">The N queens problem</a>
%K A062164 nonn,nice,more
%O A062164 1,7
%A A062164 _Matthias Engelhardt_
%E A062164 Updated link that is transferred from people.freenet.de/nQueens to www.nqueens.de _Matthias Engelhardt_, Apr 21 2010