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A145957 Number of n X n binary arrays symmetric about the diagonal and under 90-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, 1, 1, 1, 1, 1, 3, 3, 9, 9, 23, 23, 125, 125, 821, 821, 6239, 6239, 71403, 71403, 1048093, 1048093, 19913069, 19913069, 517074745, 517074745, 17642361171, 17642361171 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

Maximal 9 X 9 example:

  0 0 1 0 0 0 1 0 0

  0 0 1 1 0 1 1 0 0

  1 1 0 1 0 1 0 1 1

  0 1 1 0 0 0 1 1 0

  0 0 0 0 0 0 0 0 0

  0 1 1 0 0 0 1 1 0

  1 1 0 1 0 1 0 1 1

  0 0 1 1 0 1 1 0 0

  0 0 1 0 0 0 1 0 0

CROSSREFS

Sequence in context: A146394 A147510 A146474 * A214439 A128019 A108411

Adjacent sequences:  A145954 A145955 A145956 * A145958 A145959 A145960

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved

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Last modified May 18 14:41 EDT 2022. Contains 353816 sequences. (Running on oeis4.)