A281472 Number of 4 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.

8, 81, 60, 96, 130, 176, 260, 406, 636, 996, 1586, 2552, 4108, 6614, 10676, 17260, 27906, 45120, 72980, 118070, 191020, 309044, 500018, 809032, 1309020, 2118006, 3426980, 5544956, 8971906, 14516816, 23488676, 38005462, 61494108, 99499524

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) + a(n-3) - a(n-5) for n>9.

Empirical g.f.: x*(8 + 65*x - 94*x^2 + 49*x^3 - 83*x^4 - 40*x^5 + 23*x^6 - 8*x^7 + 4*x^8) / ((1 - x)*(1 + x^2)*(1 - x - x^2)). - Colin Barker, Feb 19 2019

Example

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

Crossrefs

Row 4 of A281469.

Sequence in context: A193943 A067449 A302974 * A302625 A078292 A210134

Adjacent sequences: A281469 A281470 A281471 * A281473 A281474 A281475

Keyword

nonn

Author

R. H. Hardin, Jan 22 2017

Status

approved