A235566 Number of (n+1) X (1+1) 0..1 arrays with the difference of the upper and lower median value of each 2 X 2 subblock in lexicographically nondecreasing order rowwise and columnwise.

16, 50, 144, 398, 1076, 2866, 7560, 19798, 51580, 133850, 346320, 894014, 2303876, 5929090, 15242904, 39155878, 100520716, 257930666, 661586400, 1696454798, 4349091860, 11147493970, 28569027240, 73209334774, 187586107036

Offset

1,1

Comments

Column 1 of A235573.

Links

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

Formula

Empirical: a(n) = 4*a(n-1) - a(n-2) - 10*a(n-3) + 8*a(n-4).

Empirical g.f.: 2*x*(8 - 7*x - 20*x^2 + 16*x^3) / ((1 - x)*(1 - 2*x)*(1 - x - 4*x^2)). - Colin Barker, Mar 19 2018

Example

Some solutions for n=5:
..1..1....1..1....1..0....0..0....0..0....0..1....0..0....0..0....0..1....1..0
..1..1....1..1....0..0....0..1....0..0....0..0....1..0....0..1....1..1....1..1
..0..1....1..0....1..0....1..1....0..1....1..0....1..1....1..1....0..1....0..1
..1..1....1..1....0..1....1..0....1..1....1..1....1..1....1..1....0..1....1..0
..0..1....0..1....1..0....0..1....1..1....1..0....0..1....1..0....1..0....0..1
..0..0....1..0....0..1....0..1....1..0....1..1....0..0....1..0....0..1....0..1

Crossrefs

Cf. A235573.

Sequence in context: A235962 A235573 A186850 * A186842 A231840 A199809

Adjacent sequences: A235563 A235564 A235565 * A235567 A235568 A235569

Keyword

nonn

Author

R. H. Hardin, Jan 12 2014

Status

approved