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A269202 Number of 2 X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three no more than once. 1
16, 180, 1284, 9612, 68052, 472044, 3212820, 21562476, 143085588, 940780908, 6138286356, 39791327340, 256517615124, 1645723601772, 10514049071892, 66922539204204, 424564703856660, 2685565034934636, 16942451080369428 (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) = 10*a(n-1) - 13*a(n-2) - 60*a(n-3) - 36*a(n-4).

Conjectures from Colin Barker, Jan 20 2019: (Start)

G.f.: 4*x*(4 + 5*x - 77*x^2 + 18*x^3) / ((1 + x)^2*(1 - 6*x)^2).

a(n) = (6*(-678*(-1)^n+335*6^n) + 56*(144*(-1)^n+25*6^n)*n) / 1029.

(End)

EXAMPLE

Some solutions for n=4:

..2..3..2..0. .1..0..0..0. .3..0..2..3. .0..3..3..1. .0..2..3..2

..2..3..1..1. .0..0..2..1. .2..2..2..0. .1..1..3..1. .3..1..0..1

CROSSREFS

Row 2 of A269201.

Sequence in context: A181239 A021084 A227557 * A269103 A016305 A218895

Adjacent sequences:  A269199 A269200 A269201 * A269203 A269204 A269205

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 20 2016

STATUS

approved

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Last modified September 19 17:35 EDT 2021. Contains 347564 sequences. (Running on oeis4.)