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A297219 Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 neighboring 1s. 1
3, 8, 24, 68, 196, 564, 1620, 4660, 13396, 38516, 110740, 318388, 915412, 2631924, 7567124, 21756468, 62552660, 179847028, 517083540, 1486682292, 4274404564, 12289467892, 35333815316, 101589305140, 292082437972, 839774919796 (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) = a(n-1) + 4*a(n-2) + 4*a(n-3).

Empirical g.f.: x*(3 + 5*x + 4*x^2) /  (1 - x - 4*x^2 - 4*x^3). - Colin Barker, Feb 26 2019

EXAMPLE

Some solutions for n=7:

..0..0..0. .0..1..1. .1..1..0. .0..0..0. .0..1..0. .1..1..0. .1..1..0

..1..1..0. .0..0..1. .0..0..0. .0..1..1. .1..0..1. .0..0..0. .0..0..0

..0..0..0. .0..1..0. .0..1..0. .0..0..0. .0..1..0. .0..1..1. .1..1..0

..0..1..0. .0..1..1. .1..0..0. .1..1..0. .0..0..0. .0..0..0. .0..0..0

..1..0..0. .0..0..0. .1..1..0. .0..1..1. .0..1..1. .0..1..0. .0..1..1

..0..1..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .1..0..0. .0..0..1

..1..0..0. .0..0..0. .0..0..0. .0..1..1. .1..1..0. .0..1..1. .0..1..0

CROSSREFS

Column 3 of A297224.

Sequence in context: A176904 A056332 A091588 * A018046 A095125 A078055

Adjacent sequences:  A297216 A297217 A297218 * A297220 A297221 A297222

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 27 2017

STATUS

approved

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Last modified October 18 00:09 EDT 2019. Contains 328135 sequences. (Running on oeis4.)