A278274 Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.

0, 2, 5, 16, 49, 153, 476, 1483, 4619, 14388, 44817, 139601, 434844, 1354499, 4219139, 13142228, 40936825, 127514425, 397195644, 1237227707, 3853849915, 12004386164, 37392552993, 116474345313, 362806816604, 1130109689139, 3520187193395

Offset

1,2

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3) for n>4.

Empirical g.f.: x^2*(1 - x)*(2 + x) / (1 - 3*x - x^2 + 2*x^3). - Colin Barker, Feb 09 2019

Example

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

Crossrefs

Column 2 of A278280.

Sequence in context: A005497 A148381 A334293 * A148382 A148383 A148384

Adjacent sequences: A278271 A278272 A278273 * A278275 A278276 A278277

Keyword

nonn

Author

R. H. Hardin, Nov 16 2016

Status

approved