A280436 Number of nX4 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.

2, 20, 42, 80, 138, 232, 386, 640, 1062, 1764, 2934, 4884, 8134, 13548, 22562, 37560, 62498, 103936, 172746, 286936, 476318, 790220, 1310222, 2171180, 3595918, 5952452, 9848346, 16286240, 26920122, 44477464, 73454354, 121259824, 200099094

Offset

1,1

Comments

Column 4 of A280440.

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.: 2*x + 2*x^2*(10-19*x-4*x^2+13*x^3+x^5+2*x^4) / ( (x-1)^2*(x^2+x-1)^2 ). - R. J. Mathar, Jan 04 2017

Example

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

Crossrefs

Cf. A280440.

Sequence in context: A293930 A357485 A194999 * A266842 A254542 A202602

Adjacent sequences: A280433 A280434 A280435 * A280437 A280438 A280439

Keyword

nonn

Author

R. H. Hardin, Jan 03 2017

Status

approved