A269053 Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once.

9, 42, 102, 360, 1068, 3288, 9864, 29472, 87312, 257184, 753504, 2197632, 6383808, 18478464, 53318784, 153414144, 440293632, 1260710400, 3602253312, 10273007616, 29245172736, 83119822848, 235886217216, 668491456512, 1892026552320

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4).

Empirical g.f.: 3*x*(3 + 2*x - 22*x^2 + 8*x^3) / (1 - 2*x - 2*x^2)^2. - Colin Barker, Jan 18 2019

Example

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

Crossrefs

Row 2 of A269052.

Sequence in context: A075233 A062783 A172464 * A027441 A000971 A061927

Adjacent sequences: A269050 A269051 A269052 * A269054 A269055 A269056

Keyword

nonn

Author

R. H. Hardin, Feb 18 2016

Status

approved