A210929 - OEIS

A210929

Number of n X n 0..3 symmetric matrices with every element equal to zero, two or four horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order.

1, 3, 42, 2316, 320744, 106842320, 85415568160, 163885278844480, 754594332585922688, 8337847863812427968768, 221082535444417970063262208

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

Some solutions for n=4:

..0..0..1..3....0..1..0..1....0..1..0..2....0..1..2..3....0..1..3..0

..0..0..2..1....1..2..3..2....1..0..2..3....1..0..3..2....1..2..0..2

..1..2..0..2....0..3..0..0....0..2..0..2....2..3..2..3....3..0..2..1

..3..1..2..1....1..2..0..0....2..3..2..3....3..2..3..0....0..2..1..3

CROSSREFS

Sequence in context: A333323 A331705 A156108 * A083402 A145984 A213956

Adjacent sequences: A210926 A210927 A210928 * A210930 A210931 A210932

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 29 2012

EXTENSIONS

Name corrected by Andrew Howroyd, Mar 25 2025

STATUS

approved