A269290 Number of 2 X n 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three no more than once.

16, 216, 2124, 19188, 164556, 1363572, 11026764, 87559668, 685523916, 5306911092, 40706083404, 309846524148, 2343253251276, 17623065834612, 131903512372044, 983118947312628, 7300393156146636, 54032675767734132, 398738196097092684

Offset

1,1

Links

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

Formula

Empirical: a(n) = 14*a(n-1) - 49*a(n-2) for n>4.

Conjectures from Colin Barker, Jan 21 2019: (Start)

G.f.: 4*x*(4 - 2*x - 29*x^2 + 9*x^3) / (1 - 7*x)^2.

a(n) = 36 * 7^(n-4) * (120*n+53) for n>2.

(End)

Example

Some solutions for n=4:
..0..0..2..1. .1..0..1..3. .1..3..2..2. .2..0..2..2. .3..1..3..2
..2..2..3..3. .1..1..2..2. .3..2..2..0. .1..0..3..1. .0..3..2..0

Crossrefs

Row 2 of A269289.

Sequence in context: A125473 A245828 A239096 * A297098 A159739 A181247

Adjacent sequences: A269287 A269288 A269289 * A269291 A269292 A269293

Keyword

nonn

Author

R. H. Hardin, Feb 21 2016

Status

approved