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A146050 Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation. 0
1, 1, 1, 1, 1, 3, 9, 19, 37, 115, 481, 2395, 10969, 57003, 371055, 2992969, 26653005, 266091447, 3019768963, 42043911685, 666291390951, 12240477419651, 251570549673017, 6156133419360705, 172490682719945137 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

Maximal 8 X 8 example

.0.0.0.0.1.1.0.0

.0.0.0.0.1.1.0.0

.0.0.0.0.1.0.1.1

.0.0.0.0.0.1.1.1

.1.1.1.0.0.0.0.0

.1.1.0.1.0.0.0.0

.0.0.1.1.0.0.0.0

.0.0.1.1.0.0.0.0

CROSSREFS

Sequence in context: A293058 A294367 A146694 * A147500 A115238 A005994

Adjacent sequences:  A146047 A146048 A146049 * A146051 A146052 A146053

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved

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Last modified February 22 19:30 EST 2018. Contains 299469 sequences. (Running on oeis4.)