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A296322 Number of n X 3 0..1 arrays with each 1 horizontally, vertically or antidiagonally adjacent to 2 neighboring 1s. 1
1, 5, 11, 23, 54, 122, 278, 634, 1438, 3274, 7451, 16943, 38547, 87691, 199477, 453789, 1032300, 2348324, 5342108, 12152500, 27645148, 62888676, 143062485, 325446157, 740342261, 1684169937, 3831239423, 8715507347, 19826499874, 45102377086 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) - a(n-2) + 4*a(n-3) - 2*a(n-4) + 4*a(n-5) - 3*a(n-6) + 2*a(n-7) - a(n-8).

Empirical g.f.: x*(1 + 3*x + 2*x^2 + 2*x^3 + x^4 - x^5 + x^6 - x^7) / ((1 + x^2)*(1 - 2*x - 2*x^3 + 2*x^4 - 2*x^5 + x^6)). - Colin Barker, Feb 23 2019

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Column 3 of A296327.

Sequence in context: A102444 A132177 A046138 * A097279 A106171 A276174

Adjacent sequences:  A296319 A296320 A296321 * A296323 A296324 A296325

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 10 2017

STATUS

approved

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Last modified February 22 18:24 EST 2020. Contains 332148 sequences. (Running on oeis4.)