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A145959 Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a zee 1,1 1,2 2,2 2,3 in any orientation. 0
1, 1, 1, 5, 17, 75, 405, 2821, 26895, 365651, 6440881, 149278281, 4554728635, 183204987539, 9796495036771, 702723336742467 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..16.

EXAMPLE

Maximal 8 X 8 example

.0.1.1.0.0.0.1.0

.1.1.0.0.1.0.1.1

.0.0.0.1.1.0.0.1

.1.1.0.1.0.1.1.0

.0.1.1.0.1.0.1.1

.1.0.0.1.1.0.0.0

.1.1.0.1.0.0.1.1

.0.1.0.0.0.1.1.0

CROSSREFS

Sequence in context: A149734 A149735 A149736 * A126956 A149737 A149738

Adjacent sequences:  A145956 A145957 A145958 * A145960 A145961 A145962

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved

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Last modified December 10 23:13 EST 2019. Contains 329909 sequences. (Running on oeis4.)