A251270 Number of (3+1) X (n+1) 0..1 arrays with no 2 X 2 subblock having x11-x00 less than x10-x01.

108, 480, 1667, 4930, 13052, 31936, 73805, 163604, 351804, 740008, 1532159, 3136950, 6372636, 12876648, 25924809, 52069752, 104417740, 209182288, 418791387, 838101930, 1676828540, 3354401200, 6709680485, 13420387996

Offset

1,1

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 35*a(n-2) + 77*a(n-3) - 105*a(n-4) + 91*a(n-5) - 49*a(n-6) + 15*a(n-7) - 2*a(n-8).

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

G.f.: x*(108 - 492*x + 1127*x^2 - 1589*x^3 + 1407*x^4 - 769*x^5 + 238*x^6 - 32*x^7) / ((1 - x)^7*(1 - 2*x)).

a(n) = (5760*(25*2^(1 + n)-49) - 186828*n - 57236*n^2 - 9885*n^3 - 905*n^4 - 27*n^5 + n^6) / 360.

(End)

Example

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

Crossrefs

Row 3 of A251268.

Sequence in context: A202435 A202428 A224526 * A255083 A063880 A059436

Adjacent sequences: A251267 A251268 A251269 * A251271 A251272 A251273

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved