This site is supported by donations to The OEIS Foundation.



Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A051567 Consider problem of placing N queens on an n X n board so that each queen attacks precisely k others. Here k=1 and sequence gives number of inequivalent solutions when N is equal to the upper bound 2*floor(2n/3). 14
0, 5, 0, 2, 149, 49, 1, 12897, 2238 (list; graph; refs; listen; history; text; internal format)



a(n) = 0 if N does not achieve 2*floor(2n/3).


M. Gardner, The Last Recreations, Springer, 1997, p. 282.

M. Gardner, The Colossal Book of Mathematics, 2001, p. 209.


Table of n, a(n) for n=3..11.

Martin Gardner, The Last Recreations, 1997

Vaclav Kotesovec, The unique solution for chessboard 9 X 9

Manfred Scheucher, C Code


Cf. A051568-A051571, A051754-A051759, A019654.

The number of solutions when N takes its maximal value is A051757.

Sequence in context: A190913 A019106 A051566 * A261219 A085850 A176867

Adjacent sequences:  A051564 A051565 A051566 * A051568 A051569 A051570




N. J. A. Sloane


Description corrected by and one more term from Jud McCranie, Aug 25 2001



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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 12 01:57 EST 2019. Contains 329948 sequences. (Running on oeis4.)