A211049 - OEIS

A211049

1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors

1, 4, 48, 1232, 69944, 8897744, 2543744944, 1632807480048, 2350761948259496, 7595900369159613200, 55087633557679363709984, 896577592582670794898595216

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A024255 A211045 A296838 * A321076 A166231 A191952

Adjacent sequences: A211046 A211047 A211048 * A211050 A211051 A211052

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 30 2012

STATUS

approved