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 A210920 Number of (2n)X(2n) 0..3 symmetric matrices with every element equal to two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order 0
 1, 3, 70, 6516, 1741480, 1297416720, 2686765690144, 15449867954722880 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE All solutions for n=2 ..0..0..1..1....0..0..1..1....0..0..0..0 ..0..0..1..1....0..0..1..1....0..1..1..0 ..1..1..2..2....1..1..0..0....0..1..1..0 ..1..1..2..2....1..1..0..0....0..0..0..0 CROSSREFS Sequence in context: A322775 A338408 A277413 * A140048 A135951 A093245 Adjacent sequences: A210917 A210918 A210919 * A210921 A210922 A210923 KEYWORD nonn AUTHOR R. H. Hardin Mar 29 2012 STATUS approved

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Last modified November 28 17:22 EST 2022. Contains 358421 sequences. (Running on oeis4.)