A180763 Half the number of n X 3 binary arrays with each element equal to at least one neighbor.

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

R. H. Hardin, Table of n, a(n) for n=1..99

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

Adjacent sequences: A180760 A180761 A180762 * A180764 A180765 A180766

Keyword

nonn

Author

R. H. Hardin, Sep 20 2010

Status

approved