A278151 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) (1,-1) or (1,0), with upper left element zero.

0, 2, 7, 22, 75, 254, 859, 2906, 9831, 33258, 112511, 380622, 1287635, 4356038, 14736371, 49852786, 168650767, 570541458, 1930127927, 6529576006, 22089397403, 74727896142, 252802661835, 855225279050, 2893206395127, 9787647126266

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) + a(n-3) for n>4.

Empirical g.f.: x^2*(2 - x)*(1 + x) / (1 - 3*x - x^2 - x^3). - Colin Barker, Feb 07 2019

Example

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

Crossrefs

Column 2 of A278157.

Sequence in context: A151439 A204218 A007141 * A090831 A174403 A119975

Adjacent sequences: A278148 A278149 A278150 * A278152 A278153 A278154

Keyword

nonn

Author

R. H. Hardin, Nov 13 2016

Status

approved