A268623 Number of n X 3 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.

24, 174, 1086, 6300, 34890, 187224, 982086, 5063964, 25764066, 129678528, 646978302, 3204131172, 15769455258, 77195600520, 376136512950, 1825265294892, 8825528262738, 42536536932432, 204425809550958, 979908028544244

Offset

1,1

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4).

Empirical g.f.: 6*x*(4 - 11*x + 7*x^2 + x^3) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 14 2019

Example

Some solutions for n=6:
..0..0..1. .0..0..0. .2..2..1. .1..0..1. .1..2..1. .1..0..1. .1..0..1
..0..1..2. .1..0..0. .0..1..2. .0..0..0. .0..1..2. .0..1..2. .0..0..0
..2..2..2. .0..1..0. .1..0..1. .1..0..0. .0..0..1. .1..0..1. .1..1..0
..1..2..2. .1..2..1. .0..1..0. .0..0..1. .1..0..0. .2..1..0. .0..0..0
..2..1..2. .0..1..0. .1..0..1. .2..1..0. .2..2..1. .2..0..1. .1..0..0
..1..2..2. .0..1..0. .0..1..2. .1..0..1. .1..2..2. .2..1..2. .2..1..0

Crossrefs

Column 3 of A268628.

Sequence in context: A221069 A272125 A166756 * A209716 A209709 A209986

Adjacent sequences: A268620 A268621 A268622 * A268624 A268625 A268626

Keyword

nonn

Author

R. H. Hardin, Feb 09 2016

Status

approved