A237630 Number of (n+1) X (1+1) 0..2 arrays with the upper median of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.

81, 260, 702, 1786, 4621, 11936, 30656, 77576, 200452, 515424, 1325424, 3365664, 8687760, 22278912, 57336960, 145904256, 376379712, 963592704, 2481143040, 6321940992, 16301843712, 41692741632, 107387375616, 273842325504

Offset

1,1

Links

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

Formula

Empirical: a(n) = 36*a(n-4) + 48*a(n-6) for n>9.

Empirical g.f.: x*(81 + 260*x + 702*x^2 + 1786*x^3 + 1705*x^4 + 2576*x^5 + 1496*x^6 + 800*x^7 + 400*x^8) / (1 - 36*x^4 - 48*x^6). - Colin Barker, Oct 23 2018

Example

Some solutions for n=5:
..2..2....0..0....2..2....2..0....2..2....1..2....0..1....2..2....2..0....2..1
..0..1....1..0....1..1....1..2....0..1....2..0....0..0....1..2....1..2....0..0
..2..0....0..2....0..0....0..0....2..1....1..0....1..2....1..0....0..0....2..0
..0..2....2..1....1..0....1..0....1..2....0..0....0..2....0..0....0..2....0..1
..1..0....0..0....2..1....0..2....0..0....2..1....1..1....2..1....1..0....0..0
..0..0....0..2....2..1....1..2....0..1....2..2....2..2....1..2....2..2....1..1

Crossrefs

Column 1 of A237637.

Sequence in context: A361179 A340697 A237637 * A236746 A236739 A237234

Adjacent sequences: A237627 A237628 A237629 * A237631 A237632 A237633

Keyword

nonn

Author

R. H. Hardin, Feb 10 2014

Status

approved