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A227328 Number of n X n 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X (n+1) binary array having two adjacent 1's and two adjacent 0's, with rows and columns of the latter in lexicographically nondecreasing order. 0
2, 11, 153, 4917, 366606, 66730314, 31357593706 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Diagonal of A227333.

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

Some solutions for n=4

..0..0..0..0....0..0..1..0....0..1..1..1....0..0..1..0....0..1..1..0

..0..0..0..0....1..1..0..0....1..0..1..1....0..0..1..0....0..1..1..0

..1..0..1..0....0..1..0..0....0..0..1..1....1..0..1..0....1..0..1..1

..0..1..0..0....0..0..0..0....0..1..0..0....1..0..0..1....0..0..1..0

CROSSREFS

Cf. A227333.

Sequence in context: A171184 A297676 A049462 * A287149 A188684 A143875

Adjacent sequences:  A227325 A227326 A227327 * A227329 A227330 A227331

KEYWORD

nonn

AUTHOR

R. H. Hardin Jul 07 2013

STATUS

approved

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Last modified February 25 12:53 EST 2021. Contains 341607 sequences. (Running on oeis4.)