A186817 Half the number of (n+2) X 3 binary arrays with each 3 X 3 subblock having sum 4 or 5.

126, 606, 2904, 14229, 70767, 351549, 1750896, 8730234, 43522407, 217032372, 1082345247, 5397586308, 26918218566, 134243793585, 669486128850, 3338798653422, 16650942997338, 83040015704427, 414129463721703

Offset

1,1

Comments

Column 1 of A186825.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 3*a(n-1) + 9*a(n-2) + 15*a(n-3) - 36*a(n-4) - 72*a(n-5) - 27*a(n-6) - 81*a(n-7).

Empirical g.f.: 3*x*(42 + 76*x - 16*x^2 - 609*x^3 - 870*x^4 - 495*x^5 - 837*x^6) / (1 - 3*x - 9*x^2 - 15*x^3 + 36*x^4 + 72*x^5 + 27*x^6 + 81*x^7). - Colin Barker, Apr 19 2018

Example

Some solutions for 4 X 3 with a(1,1)=0:
..0..1..0....0..1..0....0..1..0....0..0..1....0..0..1....0..1..0....0..0..1
..0..0..1....0..1..1....1..0..1....1..1..1....1..0..0....1..0..1....0..1..1
..0..1..1....0..1..0....0..0..1....0..0..0....0..1..1....0..1..1....0..1..0
..0..0..1....1..0..0....0..0..1....1..0..0....0..1..0....1..0..0....1..0..1

Crossrefs

Cf. A186825.

Sequence in context: A267566 A165023 A186825 * A107658 A181254 A004008

Adjacent sequences: A186814 A186815 A186816 * A186818 A186819 A186820

Keyword

nonn

Author

R. H. Hardin, Feb 27 2011

Status

approved