A210907 Number of n X n 0..2 symmetric matrices with every element equal to one, two or four horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order.

0, 1, 2, 51, 1726, 153098, 28152650, 11567939904, 10468180657260, 20883980738963652, 92033224229940826385, 894504588855167462245204

Offset

1,3

Links

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

Example

Some solutions for n=4:
..0..0..1..1....0..0..0..0....0..0..0..0....0..0..2..2....0..0..1..2
..0..0..2..0....0..1..1..0....0..1..1..0....0..1..1..2....0..0..1..2
..1..2..2..0....0..1..1..0....0..1..2..2....2..1..1..1....1..1..1..0
..1..0..0..0....0..0..0..0....0..0..2..2....2..2..1..1....2..2..0..0

Crossrefs

Sequence in context: A106042 A222850 A089304 * A099368 A132492 A030264

Adjacent sequences: A210904 A210905 A210906 * A210908 A210909 A210910

Keyword

nonn,more

Author

R. H. Hardin, Mar 29 2012

Extensions

Name corrected by Andrew Howroyd, Mar 25 2025

Status

approved