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A180763
Half the number of n X 3 binary arrays with each element equal to at least one neighbor.
1
1, 11, 63, 390, 2385, 14621, 89602, 549125, 3365327, 20624430, 126397089, 774626021, 4747304792, 29093913597, 178302394173, 1092728334730, 6696798543441, 41041409200977, 251522762447718, 1541460229095645
OFFSET
1,2
COMMENTS
Column 3 of A180771.
LINKS
FORMULA
Empirical: a(n) = 5*a(n-1) + 8*a(n-2) - 5*a(n-3) - 10*a(n-4) - a(n-5) + 3*a(n-6) + 4*a(n-7) - 2*a(n-8).
Empirical g.f.: x*(1 - x)*(1 + 7*x + 7*x^2 - x^3 - 5*x^4 - 3*x^5 + 2*x^6) / (1 - 5*x - 8*x^2 + 5*x^3 + 10*x^4 + x^5 - 3*x^6 - 4*x^7 + 2*x^8). - Colin Barker, Mar 26 2018
CROSSREFS
Cf. A180771.
Sequence in context: A120723 A053367 A163706 * A362164 A357959 A285361
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 20 2010
STATUS
approved