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

Author

R. H. Hardin, Sep 20 2010

Keywords

• nonn

Comments

Column 3 of A180771.

Links

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

Crossrefs

Cf. A180771.

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