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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A018803 Number of ways to color cells of an n X n square with 2 colors so that no subsquare of side > 1 has all corners same color. 1
1, 2, 14, 276, 10980, 781712, 58339148, 3066831440, 58170992144, 313031791856, 109957124552, 5020721992, 3980056, 1140264, 232228 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

There is no solution for a 15 X 15 (or larger) square. - Sean A. Irvine, Feb 13 2019

LINKS

Table of n, a(n) for n=0..14.

R. Bacher and S. Eliahou, Extremal binary matrices without constant 2-squares (see p. 11).

R. Bacher and S. Eliahou, Extremal binary matrices without constant 2-squares, The Electronic Journal of Combinatorics, Open Journal Systems, 2010, 1 (1), pp.77-100. See p. 87.

CROSSREFS

Main diagonal of A255256.

Sequence in context: A015197 A156910 A279117 * A217474 A132695 A015015

Adjacent sequences:  A018800 A018801 A018802 * A018804 A018805 A018806

KEYWORD

nonn,fini,full

AUTHOR

David W. Wilson

EXTENSIONS

a(0)=1 from Alois P. Heinz, Feb 19 2015

More terms from Bacher and Eliahou paper added by Sean A. Irvine, Feb 13 2019

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 24 22:46 EDT 2021. Contains 347651 sequences. (Running on oeis4.)