A281471 Number of 3 X n 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors and with new values introduced in order 0 sequentially upwards.

4, 25, 24, 39, 57, 87, 145, 241, 397, 669, 1133, 1909, 3229, 5477, 9277, 15717, 26653, 45189, 76605, 129893, 220253, 373445, 633213, 1073701, 1820573, 3086981, 5234365, 8875493, 15049437, 25518149, 43269117, 73367973, 124404253, 210942469

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) - a(n-2) + 2*a(n-3) - 2*a(n-4) for n>8.

Empirical g.f.: x*(4 + 17*x - 22*x^2 + 8*x^3 - 39*x^4 + 14*x^5 - 2*x^6 + 2*x^7) / ((1 - x)*(1 - x - 2*x^3)). - Colin Barker, Feb 19 2019

Example

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

Crossrefs

Row 3 of A281469.

Sequence in context: A111446 A114390 A114392 * A107734 A302624 A238515

Adjacent sequences: A281468 A281469 A281470 * A281472 A281473 A281474

Keyword

nonn

Author

R. H. Hardin, Jan 22 2017

Status

approved