A253437 Number of (3+1) X (n+1) 0..1 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally, vertically and ne-to-sw antidiagonally.

69, 73, 85, 120, 192, 336, 624, 1200, 2352, 4656, 9264, 18480, 36912, 73776, 147504, 294960, 589872, 1179696, 2359344, 4718640, 9437232, 18874416, 37748784, 75497520, 150994992, 301989936, 603979824, 1207959600, 2415919152, 4831838256

Offset

1,1

Links

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

Formula

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

Empirical: a(n) = 9*2^(n-1) + 48 for n>3.

Empirical g.f.: x*(69 - 134*x + 4*x^2 + 11*x^3 + 2*x^4) / ((1 - x)*(1 - 2*x)). - Colin Barker, Dec 12 2018

Example

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

Crossrefs

Row 3 of A253435.

Sequence in context: A253430 A256694 A166067 * A325386 A260428 A168477

Adjacent sequences: A253434 A253435 A253436 * A253438 A253439 A253440

Keyword

nonn

Author

R. H. Hardin, Dec 31 2014

Status

approved