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A282371
Number of n X 2 0..1 arrays with no 1 equal to more than four of its king-move neighbors, with the exception of exactly two elements.
1
0, 0, 1, 6, 33, 168, 810, 3780, 17226, 77112, 340443, 1486458, 6431643, 27619056, 117846900, 500088168, 2112085044, 8883220752, 37225117269, 155483824590, 647540441397, 2689724482776, 11145934772190, 46087885526508
OFFSET
1,4
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) - 3*a(n-2) - 12*a(n-3) - 27*a(n-4) - 18*a(n-5) - 9*a(n-6).
Empirical g.f.: x^3 / (1 - 3*x - 3*x^2 - 3*x^3)^2. - Colin Barker, Feb 20 2019
EXAMPLE
All solutions for n=4:
..1..1. .0..1. .1..1. .1..0. .0..0. .1..1
..1..1. .1..1. .1..1. .1..1. .1..1. .1..1
..1..1. .1..1. .1..1. .1..1. .1..1. .1..1
..1..0. .1..1. .0..0. .1..1. .1..1. .0..1
CROSSREFS
Column 2 of A282377.
Sequence in context: A099432 A072260 A281930 * A291004 A203155 A084153
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 13 2017
STATUS
approved