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A278171
Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,0) (-1,1) (0,-1) (0,1) (1,-1) or (1,0), with upper left element zero.
1
0, 2, 5, 13, 43, 137, 436, 1394, 4458, 14258, 45607, 145888, 466673, 1492823, 4775347, 15275728, 48865129, 156313412, 500027005, 1599523726, 5116675993, 16367605483, 52357919474, 167486425305, 535768092953, 1713855012003, 5482407483581
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 3*a(n-4) - 2*a(n-5) - a(n-6) for n>7.
Empirical g.f.: x^2*(1 + x)*(2 - 3*x - x^2 + x^4) / (1 - 3*x - x^2 + 3*x^4 + 2*x^5 + x^6). - Colin Barker, Feb 08 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..0
..0..1. .0..1. .0..1. .1..1. .0..1. .1..1. .0..1. .1..1. .1..0. .1..1
..0..1. .1..1. .1..0. .0..0. .0..0. .1..0. .0..1. .0..1. .1..0. .1..1
..0..0. .0..0. .1..0. .1..1. .1..1. .1..0. .0..1. .0..1. .1..1. .0..0
CROSSREFS
Column 2 of A278177.
Sequence in context: A192745 A299430 A307263 * A212824 A338660 A286949
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 13 2016
STATUS
approved