The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A051906 Number of ways of placing n nonattacking queens on an n X n toroidal chessboard. 6
 1, 0, 0, 0, 10, 0, 28, 0, 0, 0, 88, 0, 4524, 0, 0, 0, 140692, 0, 820496, 0, 0, 0, 128850048, 0, 1957725000, 0, 0, 0, 605917055356, 0, 13404947681712, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS The sequence has been computed up to n = 23 by Rivin, Vardi & Zimmermann, see p. 637 of their paper from 1994. Further terms were calculated by the submitter, Dec 17 1999 and Jan 11 2001. a(n) is divisible by n. Only terms indexed by odd numbers coprime to 3 are nonzero, therefore A007705(n) = a(2n+1) is the main entry. - M. F. Hasler, Jul 01 2019 LINKS M. R. Engelhardt, A group-based search for solutions of the n-queens problem, Discr. Math., 307 (2007), 2535-2551. V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 62-63. Kevin Pratt, Closed-Form Expressions for the n-Queens Problem and Related Problems, arXiv:1609.09585 [cs.DM], 2016. I. Rivin, I. Vardi and P. Zimmermann, The n-queens problem, Amer. Math. Monthly, 101 (1994), 629-639. CROSSREFS See A007705, which is the main entry for this sequence. Sequence in context: A107781 A107772 A087474 * A171809 A167302 A302576 Adjacent sequences:  A051903 A051904 A051905 * A051907 A051908 A051909 KEYWORD nonn,nice,hard,more AUTHOR Matthias Engelhardt, Dec 17 1999 EXTENSIONS Term a(31) added from A007705 by Vaclav Kotesovec, Aug 25 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)