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A210897
Number of (2n)X(2n) 0..2 symmetric matrices with every element equal to two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
0
1, 3, 35, 792, 34547, 2902490, 468761578, 145469326676, 86673425993599
OFFSET
1,2
EXAMPLE
All solutions for n=2
..0..0..0..0....0..0..1..1....0..0..1..1
..0..1..1..0....0..0..1..1....0..0..1..1
..0..1..1..0....1..1..2..2....1..1..0..0
..0..0..0..0....1..1..2..2....1..1..0..0
CROSSREFS
Sequence in context: A093531 A129505 A185752 * A377745 A267221 A135516
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved