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A145777 Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only either two adjacent vertically or two adjacent horizontally. 0
1, 1, 1, 2, 4, 7, 20, 66, 223, 972, 5286, 31417, 228724, 2000916, 20634823, 248726975, 3651917796, 62467383723, 1283523230287, 30987743547862, 900690199090722, 30606347558434592, 1253939853475088497, 60154380091248350142 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..24.

CROSSREFS

Sequence in context: A327444 A291403 A101805 * A188497 A237759 A306978

Adjacent sequences:  A145774 A145775 A145776 * A145778 A145779 A145780

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 18 2008

STATUS

approved

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Last modified March 30 12:10 EDT 2020. Contains 333125 sequences. (Running on oeis4.)