A204610 Number of (n+1) X 3 0..1 arrays with the determinants of 2 X 2 subblocks nondecreasing rightwards and downwards.

47, 181, 749, 3254, 14199, 62031, 271125, 1185255, 5181921, 22656123, 99057573, 433104831, 1893650697, 8279562627, 36200555181, 158278967559, 692040086289, 3025793769291, 13229621235765, 57843625143375, 252908600485401

Offset

1,1

Comments

Column 2 of A204616.

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 5*a(n-2) - 12*a(n-3) + 12*a(n-4) for n>7.

Empirical g.f.: x*(47 - 101*x - 102*x^2 + 229*x^3 + 28*x^4 - 77*x^5 - 6*x^6) / ((1 - x)*(1 - 2*x)*(1 - 3*x - 6*x^2)). - Colin Barker, Jun 07 2018

Example

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

Crossrefs

Cf. A204616.

Sequence in context: A253351 A253344 A227282 * A158632 A142413 A065532

Adjacent sequences: A204607 A204608 A204609 * A204611 A204612 A204613

Keyword

nonn

Author

R. H. Hardin, Jan 17 2012

Status

approved