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A295091 Number of n X 2 0..1 arrays with each 1 horizontally or vertically adjacent to 1 or 3 1s. 4
2, 5, 11, 24, 55, 123, 276, 621, 1395, 3134, 7043, 15825, 35558, 79899, 179531, 403402, 906437, 2036745, 4576524, 10283357, 23106493, 51919818, 116662773, 262138871, 589020696, 1323517491, 2973916807, 6682330408, 15015060133, 33738533867 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Column 2 of A295097.
LINKS
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) + 2*a(n-3) - a(n-5).
Empirical g.f.: x*(2 + 3*x + 2*x^2 - x^3 - x^4) / ((1 + x + x^2)*(1 - 2*x - x^2 + x^3)). - Colin Barker, Feb 21 2018
EXAMPLE
Some solutions for n=5:
..1..0. .1..1. .0..1. .1..0. .1..0. .1..1. .0..0. .0..0. .0..0. .0..0
..1..0. .0..0. .0..1. .1..0. .1..1. .0..0. .0..0. .1..0. .1..1. .0..0
..0..0. .0..1. .0..0. .0..0. .1..0. .1..0. .1..0. .1..1. .0..0. .1..0
..1..1. .0..1. .1..0. .1..0. .0..1. .1..1. .1..1. .1..0. .1..0. .1..0
..0..0. .0..0. .1..0. .1..0. .0..1. .1..0. .1..0. .0..0. .1..0. .0..0
CROSSREFS
Cf. A295097.
Sequence in context: A018115 A242551 A018007 * A071879 A228862 A134527
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 14 2017
STATUS
approved

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Last modified April 12 14:01 EDT 2024. Contains 371635 sequences. (Running on oeis4.)