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A139012 Number of n X n symmetric binary matrices containing no more than three 1s in any 3 X 3 sub-block. 0
1, 2, 7, 20, 146, 1660, 24266, 619885, 24951532, 1491389352, 141842503743, 21156539568960, 4861988525864115, 1744688422871068399, 977626718408600885914, 851525107752786868842753 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..15.

CROSSREFS

Sequence in context: A189771 A260504 A009697 * A132605 A088157 A265316

Adjacent sequences:  A139009 A139010 A139011 * A139013 A139014 A139015

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 31 2008

STATUS

approved

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Last modified April 4 05:34 EDT 2020. Contains 333212 sequences. (Running on oeis4.)