A297309 Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 or 2 neighboring 1s.

4, 23, 117, 609, 3159, 16389, 85041, 441225, 2289339, 11878281, 61631001, 319774761, 1659164103, 8608637997, 44666257401, 231752633913, 1202457662523, 6238998904833, 32371291359585, 167959719216009, 871465613342823

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 11*a(n-2) + 3*a(n-3) - 6*a(n-4).

Empirical g.f.: x*(4 + 11*x + 4*x^2 - 7*x^3) / (1 - 3*x - 11*x^2 - 3*x^3 + 6*x^4). - Colin Barker, Feb 26 2019

Example

Some solutions for n=5:
..1..1..1. .0..1..0. .1..1..0. .0..1..0. .1..1..0. .0..0..0. .1..1..0
..0..1..0. .1..0..0. .1..1..1. .1..0..1. .1..1..0. .0..0..0. .1..1..1
..1..0..0. .1..1..1. .0..0..0. .0..1..0. .1..0..1. .0..0..0. .0..0..0
..0..0..1. .0..1..0. .1..1..1. .1..1..0. .0..1..0. .1..1..0. .0..1..0
..1..1..0. .0..1..1. .0..1..1. .0..0..0. .0..1..1. .1..1..1. .1..1..1

Crossrefs

Column 3 of A297314.

Sequence in context: A239813 A174248 A353096 * A201350 A015532 A144465

Adjacent sequences: A297306 A297307 A297308 * A297310 A297311 A297312

Keyword

nonn

Author

R. H. Hardin, Dec 28 2017

Status

approved