A192840 Number of n X n symmetric 0..1 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 1 and with new values 0..1 introduced in lower triangular row major order.

0, 0, 0, 4, 23, 183, 2051, 34480, 852316, 31436447, 1719054682, 139749375351, 16887682211104, 3032513808121100, 809442991768500675, 321179427812462958356, 189437827654558885755437, 166102021233191494352782229, 216509490023889834811985647939

Offset

1,4

Links

R. H. Hardin, Table of n, a(n) for n = 1..19

Example

Some solutions for 6 X 6:
..0..0..0..0..1..1....0..0..0..0..1..1....0..0..0..0..0..0....0..0..0..0..1..1
..0..0..0..0..1..1....0..0..0..0..1..1....0..0..0..0..0..0....0..1..1..0..1..1
..0..0..0..0..0..0....0..0..0..0..1..1....0..0..1..1..1..1....0..1..1..0..0..0
..0..0..0..1..1..0....0..0..0..1..1..1....0..0..1..1..1..1....0..0..0..1..1..0
..1..1..0..1..1..0....1..1..1..1..0..0....0..0..1..1..0..0....1..1..0..1..1..0
..1..1..0..0..0..0....1..1..1..1..0..0....0..0..1..1..0..0....1..1..0..0..0..0

Crossrefs

Sequence in context: A058863 A383985 A378090 * A302189 A292971 A317967

Adjacent sequences: A192837 A192838 A192839 * A192841 A192842 A192843

Keyword

nonn

Author

R. H. Hardin, Jul 11 2011

Status

approved