A280439 Number of n X 7 0..1 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.

20, 120, 236, 386, 574, 834, 1211, 1784, 2684, 4128, 6478, 10334, 16693, 27208, 44620, 73470, 121278, 200490, 331695, 548936, 908476, 1503260, 2486766, 4112326, 6797929, 11232984, 18554156, 30634874, 50561854, 83419218, 137578403

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) - 4*a(n-2) - 2*a(n-3) + 4*a(n-4) - a(n-6) for n>7.

Empirical g.f.: x*(20 + 40*x - 164*x^2 - 38*x^3 + 134*x^4 + 74*x^5 + 19*x^6) / ((1 - x)^2*(1 - x - x^2)^2). - Colin Barker, Feb 13 2019

Example

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

Crossrefs

Column 7 of A280440.

Sequence in context: A121040 A044352 A044733 * A093566 A213223 A041770

Adjacent sequences: A280436 A280437 A280438 * A280440 A280441 A280442

Keyword

nonn

Author

R. H. Hardin, Jan 03 2017

Status

approved