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A147128 Number of n X n binary arrays symmetric about the diagonal and under 90 degree rotation with all ones connected only in a 1000-1000-1111-1000 pattern in any orientation. 0
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 9, 9, 23, 23, 55, 55, 223 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,13

LINKS

Table of n, a(n) for n=1..21.

CROSSREFS

Sequence in context: A232023 A146695 A146442 * A147214 A146820 A146663

Adjacent sequences:  A147125 A147126 A147127 * A147129 A147130 A147131

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 04 2008

STATUS

approved

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Last modified June 28 19:10 EDT 2022. Contains 354907 sequences. (Running on oeis4.)