OFFSET
1,4
COMMENTS
From Don Knuth, Jul 17 2015: (Start)
Ahrens proved that a(n)=0 unless n=4k or 4k+1. He also proved that in the latter case, a(n) is a multiple of 2^k. He found all solutions when n was less than 20.
Kraitchik carried the calculations further (for n less than 28). In his book he tabulated only the values a(n)/2^k. He had correct entries for n=21 and n=25, but his values for n=20 and n=24 were 1 too small -- of course he had calculated everything by hand! (End)
REFERENCES
W. Ahrens, Mathematische Unterhaltungen und Spiele, 2nd edition, volume 1, Teubner, 1910, pages 249-258.
Maurice Kraitchik, Le problème des reines, Bruxelles: L'Échiquier, 1926, page 18.
LINKS
Tricia M. Brown, Kaleidoscopes, Chessboards, and Symmetry, Journal of Humanistic Mathematics, Volume 6 Issue 1 ( January 2016), pages 110-126.
P. Capstick and K. McCann, The problem of the n queens, apparently unpublished, no date (circa 1990?) [Scanned copy]
Gheorghe Coserea, Solutions for n=20.
Gheorghe Coserea, Solutions for n=24.
Gheorghe Coserea, MiniZinc model for generating solutions.
YuhPyng Shieh, Cyclic Complete Mappings Counting Problems
M. Szabo, Non-attacking Queens Problem Page
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Miklos SZABO (mike(AT)ludens.elte.hu)
EXTENSIONS
More terms from Jieh Hsiang and YuhPyng Shieh (arping(AT)turing.csie.ntu.edu.tw), May 20 2002
STATUS
approved