A251269 Number of (2+1) X (n+1) 0..1 arrays with no 2 X 2 subblock having x11-x00 less than x10-x01.

35, 114, 313, 772, 1775, 3894, 8277, 17224, 35339, 71834, 145137, 292108, 586471, 1175678, 2354637, 4713168, 9430915, 18867170, 37740521, 75488148, 150984415, 301978054, 603966533, 1207944792, 2415902715, 4831820074, 9663656417

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 14*a(n-2) + 16*a(n-3) - 9*a(n-4) + 2*a(n-5).

Conjectures from Colin Barker, Nov 27 2018: (Start)

G.f.: x*(35 - 96*x + 119*x^2 - 70*x^3 + 16*x^4) / ((1 - x)^4*(1 - 2*x)).

a(n) = 8*(9*2^n-8) - (109*n)/3 - 8*n^2 - (2*n^3)/3.

(End)

Example

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

Crossrefs

Row 2 of A251268.

Sequence in context: A183854 A156332 A110832 * A268118 A212888 A044286

Adjacent sequences: A251266 A251267 A251268 * A251270 A251271 A251272

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved