login
Number of non-isomorphic ways to attack all squares on an n X n chessboard using the smallest possible number of queens with each queen attacking at least one other.
(Formerly M1313 N0502)
1

%I M1313 N0502 #29 Dec 25 2017 11:58:13

%S 0,2,5,3,15,150,5,56,3,39,681

%N Number of non-isomorphic ways to attack all squares on an n X n chessboard using the smallest possible number of queens with each queen attacking at least one other.

%C Differs from A002563 and A002567 in that each queen is attacking at least one other queen. - _Sean A. Irvine_, Apr 05 2014

%C The Sainte-Laguë paper has "a(6)=140?". - _Sean A. Irvine_, Apr 05 2014

%D W. Ahrens, Mathematische Unterhaltungen und Spiele, second edition (1910), Vol. 1, p. 301.

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

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

%H M. A. Sainte-Laguë, <a href="https://eudml.org/doc/192551">Les Réseaux (ou Graphes)</a>, Mémorial des Sciences Mathématiques, Fasc. 18, Gauthier-Villars, Paris, 1923, 64 pages. See p. 49.

%H M. A. Sainte-Laguë, <a href="/A002560/a002560.pdf">Les Réseaux (ou Graphes)</a>, Mémorial des Sciences Mathématiques, Fasc. 18, Gauthier-Villars, Paris, 1923, 64 pages. See p. 49. [Incomplete annotated scan of title page and pages 18-51]

%Y Cf. A002566 (all solutions for attacking queens). - _Sean A. Irvine_, Apr 05 2014

%K nonn,more

%O 1,2

%A _N. J. A. Sloane_

%E a(6) corrected and a(9)-a(11) from _Sean A. Irvine_, Apr 05 2014

%E Better name from _Sean A. Irvine_, Apr 05 2014