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A180762
Half the number of nX2 binary arrays with each element equal to at least one neighbor
11
1, 3, 11, 34, 111, 361, 1172, 3809, 12377, 40218, 130687, 424661, 1379916, 4483973, 14570461, 47346034, 153848731, 499924281, 1624480652, 5278674169, 17152805697, 55737242698, 181115572487, 588526611821, 1912389796556, 6214221516093
OFFSET
1,2
COMMENTS
Column 2 of A180771
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-4).
Empirical G.f.: x*(1-x)*(1+x+2*x^2)/(1-3*x-x^2+2*x^4). [Colin Barker, Feb 22 2012]
CROSSREFS
Sequence in context: A052471 A037496 A355364 * A134326 A295546 A361435
KEYWORD
nonn
AUTHOR
R. H. Hardin Sep 20 2010
STATUS
approved