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

1, 3, 70, 6516, 1741480, 1297416720, 2686765690144, 15449867954722880

Offset

1,2

Links

Table of n, a(n) for n=1..8.

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 A361254

Adjacent sequences: A210917 A210918 A210919 * A210921 A210922 A210923

Keyword

nonn

Author

R. H. Hardin Mar 29 2012

Status

approved