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A210898 Number of n X n 0..2 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
1, 3, 17, 199, 3494, 98664, 4322895, 299203520, 32406437104, 5516394350943, 1472647280151852, 617087491407309762, 405686597596735406852 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

Some solutions for n=3

..0..1..0....0..1..0....0..1..2....0..0..1....0..1..2....0..1..2....0..1..2

..1..0..1....1..2..1....1..2..1....0..0..2....1..2..0....1..0..0....1..2..1

..0..1..2....0..1..2....2..1..0....1..2..1....2..0..1....2..0..0....2..1..2

CROSSREFS

Sequence in context: A158885 A202424 A133991 * A009494 A267659 A075271

Adjacent sequences:  A210895 A210896 A210897 * A210899 A210900 A210901

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified January 28 10:02 EST 2020. Contains 331319 sequences. (Running on oeis4.)