A206866 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 1 0 1 vertically.

7, 49, 211, 889, 3967, 17737, 78799, 350017, 1555843, 6915889, 30739447, 136629265, 607288711, 2699272273, 11997693379, 53327205481, 237028156975, 1053540057337, 4682762813455, 20813890672513, 92513343672307, 411202253906785

Offset

1,1

Comments

Column 3 of A206871.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 4*a(n-1) + 8*a(n-3) + 4*a(n-4) - 2*a(n-5) - a(n-6).

Empirical g.f.: x*(7 + 21*x + 15*x^2 - 11*x^3 - 9*x^4 - x^5) / (1 - 4*x - 8*x^3 - 4*x^4 + 2*x^5 + x^6). - Colin Barker, Jun 17 2018

Example

Some solutions for n=4:
  0 1 0    1 1 1    0 1 1    1 1 0    0 1 0    0 1 1    0 0 1
  1 0 1    1 1 0    1 1 0    0 0 1    1 0 0    0 1 1    0 0 1
  0 0 1    1 0 0    1 1 0    0 0 1    1 0 1    0 1 1    1 1 1
  0 1 0    1 0 1    1 0 1    1 0 0    1 1 0    0 1 1    0 0 1

Crossrefs

Cf. A206871.

Sequence in context: A206931 A188608 A188601 * A206872 A133047 A223639

Adjacent sequences: A206863 A206864 A206865 * A206867 A206868 A206869

Keyword

nonn

Author

R. H. Hardin, Feb 13 2012

Status

approved