A251195 Number of (n+1) X (2+1) 0..1 arrays with no 2 X 2 subblock having the minimum of its diagonal elements less than the absolute difference of its antidiagonal elements.

25, 86, 310, 1135, 4172, 15353, 56519, 208082, 766105, 2820622, 10384911, 38234978, 140772894, 518295264, 1908250809, 7025765815, 25867346793, 95237963740, 350645538289, 1291000864451, 4753185339819, 17500198099533, 64431935981585

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 7*a(n-2) - a(n-3) - 7*a(n-4) - a(n-5) for n>6.

Empirical g.f.: x*(25 + 36*x - 37*x^2 - 62*x^3 - 7*x^4 + x^5) / (1 - 2*x - 7*x^2 + x^3 + 7*x^4 + x^5). - Colin Barker, Nov 26 2018

Example

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

Crossrefs

Column 2 of A251201.

Sequence in context: A081272 A318293 A027026 * A087240 A044212 A044593

Adjacent sequences: A251192 A251193 A251194 * A251196 A251197 A251198

Keyword

nonn

Author

R. H. Hardin, Nov 30 2014

Status

approved