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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. 1
16, 216, 2124, 19188, 164556, 1363572, 11026764, 87559668, 685523916, 5306911092, 40706083404, 309846524148, 2343253251276, 17623065834612, 131903512372044, 983118947312628, 7300393156146636, 54032675767734132, 398738196097092684 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 24 11:17 EDT 2021. Contains 346273 sequences. (Running on oeis4.)