1,4

J. R. Bitner and E. M. Reingold, Backtrack programming techniques, Commun. ACM, 18 (1975), 651-656.

J. Freeman, A neural network solution to the n-queens problem, The Mathematica J., 3 (No. 3, 1993), 52-56.

M. Gardner, The Unexpected Hanging, pp. 190-2, Simon & Shuster NY 1969

Jieh Hsiang, Yuh-Pyng Shieh and Yao-Chiang Chen, The cyclic complete mappings counting problems, in Problems and Problem Sets for ATP, volume 02-10 of DIKU technical reports, G. Sutcliffe, J. Pelletier and C. Suttner, eds., 2002.

Kenji Kise, Takahiro Katagiri, Hiroki Honda and Toshitsugu Yuba: Solving the 24-queens Problem using MPI on a PC Cluster, Technical Report UEC-IS-2004-6, Graduate School of Information Systems, The University of Electro-Communications (2004)

I. Rivin, I. Vardi and P. Zimmermann, The n-queens problem, Amer. Math. Monthly, 101 (1994), 629-639.

M. A. Sainte-Lagu\"{e}, Les R\'{e}seaux (ou Graphes), M\'{e}morial des Sciences Math\'{e}matiques, Fasc. 18, Gauthier-Villars, Paris, 1926, p. 47.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

R. J. Walker, An enumerative technique for a class of combinatorial problems, pp. 91-94 of Proc. Sympos. Applied Math., vol. 10, Amer. Math. Soc., 1960.

M. B. Wells, Elements of Combinatorial Computing. Pergamon, Oxford, 1971, p. 238.

Amazing Mathematical Object Factory, Information on the n Queens problem [Link corrected by Gerry Myerson, Apr 08 2009]

Anonymous, N Queens Problem

D. Bill, Durango Bill's The N-Queens Problem [Broken link?]

Patrick GUILLEMIN, N-Queens Challenge [Broken link?]

Patrick GUILLEMIN, N-Queens Challenge [Broken link?]

Patrick GUILLEMIN, N-Queens Challenge [Broken link?]

Kenji KISE, 24-queens.

W. Kosters, n-Queens (Extensive Bibliography)

NQuens@home, Home Page

Objectweb ProActive INRIA Team, Home Page

Objectweb ProActive INRIA Team, Solve the N Queens challenge with ProActive !

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Queens(AT)TUD project website. [From Thomas B. Preusser (thomas.preusser(AT)tu-dresden.de), Jul 11 2009]

Strong conjecture : there is a constant c around 2.54 such that a(n) is asymptotic to n!/c^n; weak conjecture : lim n -> infinity (1/n) * ln(n!/a(n)) = constant =0.90.... - Benoit Cloitre (benoit7848c(AT)orange.fr), Nov 10 2002

a(2) = a(3) = 0, since on 2 X 2 and 3 X 3 chessboards there are no solutions.

See A140393 for another version. Cf. A002562, A065256.

Sequence in context: A029673 A054790 A140393 this_sequence A038216 A145911 A027626

Adjacent sequences: A000167 A000168 A000169 this_sequence A000171 A000172 A000173

nonn,hard,nice

N. J. A. Sloane (njas(AT)research.att.com).

Terms for n=21-23 computed by Sylvain PION (Sylvain.Pion(AT)sophia.inria.fr) and Joel-Yann FOURRE (Joel-Yann.Fourre(AT)ens.fr).

a(24) from Kenji KISE (kis(AT)is.uec.ac.jp), Sep 01 2004

a(25) from Objectweb ProActive INRIA Team (proactive(AT)objectweb.org), Jun 11 2005 [Communicated by Alexandre Di Costanzo (Alexandre.Di_Costanzo(AT)sophia.inria.fr)]. This calculation took about 53 years of CPU time.

a(25) has been confirmed by the NTU 25Queen Project at National Taiwan University and Ming Chuan University, led by Yuh-Pyng (Arping) Shieh, Jul 26 2005. This computation took 26613 days CPU time.

Some of the links may be broken. I would appreciate receiving updates to them. - N. J. A. Sloane (njas(AT)research.att.com), May 01 2006

The NQueens-at-Home web site gives a different value for a(24), 226732487925864. Thanks to Goran Fagerstrom for pointing this out. I do not know which value is correct. I have therefore created a new entry, A140393, which gives the NQueens-at-home version of the sequence. - N. J. A. Sloane (njas(AT)research.att.com), Jun 18 2008

It now appears that this sequence (A000170) is correct and A140393 is wrong. - N. J. A. Sloane (njas(AT)research.att.com), Nov 08 2008

Added a(26) as calculated by Queens(AT)TUD [http://queens.inf.tu-dresden.de/]. Thomas B. Preusser (thomas.preusser(AT)tu-dresden.de), Jul 11 2009