A240342 Number of n X 2 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of elements above it or three plus the sum of the elements diagonally to its northwest, modulo 4.

4, 18, 78, 334, 1418, 6002, 25374, 107230, 453098, 1914498, 8089374, 34180206, 144422410, 610231506, 2578426334, 10894689470, 46033605738, 194506954850, 821855141726, 3472605259214, 14672886589706, 61997717795634

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 4*a(n-3) + 8*a(n-4).

Empirical g.f.: 2*x*(1 + x)*(2 - 5*x + 4*x^2) / (1 - 6*x + 7*x^2 + 4*x^3 - 8*x^4). - Colin Barker, Oct 27 2018

Example

Some solutions for n=4:
..2..2....2..0....0..0....2..2....0..2....2..2....2..2....0..2....0..0....2..0
..2..0....0..2....0..2....0..0....0..2....2..0....2..0....2..2....2..2....2..0
..0..0....0..2....2..2....2..2....0..0....2..0....0..0....2..2....0..0....0..2
..0..2....2..0....2..2....0..2....0..0....0..0....2..1....2..2....0..2....0..0

Crossrefs

Column 2 of A240347.

Sequence in context: A058870 A219436 A219137 * A208309 A112619 A196810

Adjacent sequences: A240339 A240340 A240341 * A240343 A240344 A240345

Keyword

nonn

Author

R. H. Hardin, Apr 04 2014

Status

approved