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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 1
0, 0, 0, 4, 23, 183, 2051, 34480, 852316, 31436447, 1719054682, 139749375351, 16887682211104, 3032513808121100, 809442991768500675, 321179427812462958356, 189437827654558885755437 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

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

EXAMPLE

Some solutions for 6X6

..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: A106174 A056814 A058863 * A302189 A292971 A317967

Adjacent sequences:  A192837 A192838 A192839 * A192841 A192842 A192843

KEYWORD

nonn

AUTHOR

R. H. Hardin Jul 11 2011

STATUS

approved

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Last modified November 22 05:52 EST 2018. Contains 317453 sequences. (Running on oeis4.)