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A296399 Number of n X 2 0..1 arrays with each 1 horizontally, vertically or antidiagonally adjacent to 2 or 3 neighboring 1s. 1
1, 4, 8, 17, 46, 114, 289, 757, 1964, 5118, 13391, 35008, 91589, 239740, 627506, 1642656, 4300361, 11258087, 29473546, 77162161, 202011991, 528872756, 1384604934, 3624939359, 9490209947, 24845686106, 65046840605, 170294825972 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) - a(n-2) + 2*a(n-3) - 6*a(n-4) + 3*a(n-5) - 2*a(n-6) - a(n-7) - 2*a(n-8) + a(n-9).
Empirical g.f.: x*(1 + x - 3*x^2 - 5*x^3 + x^4 - 2*x^5 - 3*x^6 - x^7 + x^8) / ((1 - 3*x + x^2)*(1 - 2*x^3 - x^5 - x^6 - x^7)). - Colin Barker, Feb 23 2019
EXAMPLE
Some solutions for n=7:
..0..0. .0..0. .1..1. .1..1. .1..1. .1..1. .0..1. .0..0. .0..0. .1..1
..1..1. .0..0. .1..0. .1..1. .1..0. .1..1. .1..1. .0..1. .0..1. .1..0
..1..0. .1..1. .1..1. .0..0. .1..1. .0..0. .1..0. .1..1. .1..1. .0..0
..1..1. .1..0. .1..1. .0..0. .1..0. .0..1. .0..0. .0..1. .1..0. .0..1
..1..0. .1..0. .0..0. .0..0. .0..0. .1..1. .0..1. .1..1. .1..1. .1..1
..1..1. .1..1. .1..1. .1..1. .0..0. .0..1. .1..1. .0..0. .1..0. .0..1
..1..1. .1..0. .1..1. .1..1. .0..0. .1..1. .0..0. .0..0. .0..0. .1..1
CROSSREFS
Column 2 of A296405.
Sequence in context: A084814 A098125 A335274 * A119471 A145779 A252790
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 11 2017
STATUS
approved

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Last modified June 13 15:51 EDT 2024. Contains 373389 sequences. (Running on oeis4.)