OFFSET
2,1
REFERENCES
J. Propp, Enumeration of matchings: problems and progress, pp. 255-291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 7).
LINKS
J. Propp, Updated article
J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics
EXAMPLE
From Andrew Howroyd, Mar 07 2016: (Start)
The 2 removed squares are central and separated by a knights move.
Illustration of n = 4:
* ++
* ++++
* ++++++
* +++++ ++
* +++ ++++
* ++++++
* ++++
* ++
(End)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 28 2002
EXTENSIONS
a(11)-a(14) from Andrew Howroyd, Mar 07 2016
STATUS
approved