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.

2, 11, 153, 4917, 366606, 66730314, 31357593706

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