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A253154 Number of (n+1) X (3+1) 0..1 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally and vertically. 1
69, 88, 94, 129, 201, 345, 633, 1209, 2361, 4665, 9273, 18489, 36921, 73785, 147513, 294969, 589881, 1179705, 2359353, 4718649, 9437241, 18874425, 37748793, 75497529, 150995001, 301989945, 603979833, 1207959609, 2415919161, 4831838265 (list; graph; refs; listen; history; text; internal format)
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) + 57 for n>3.

Empirical g.f.: x*(69 - 119*x - 32*x^2 + 23*x^3 + 2*x^4) / ((1 - x)*(1 - 2*x)). - Colin Barker, Dec 09 2018

EXAMPLE

Some solutions for n=6:

..0..0..0..0....0..0..0..0....0..0..0..0....0..1..1..1....0..0..0..0

..0..0..0..0....1..1..1..1....1..1..1..1....0..0..0..0....0..0..0..0

..0..0..0..0....0..0..0..0....1..1..1..1....1..1..1..1....0..0..0..0

..0..0..0..0....0..0..0..0....0..0..0..0....1..1..1..1....0..0..0..0

..0..0..0..0....1..1..1..1....1..1..1..1....0..0..0..0....1..1..1..1

..1..1..1..1....0..0..0..0....1..1..1..1....1..1..1..1....0..0..0..0

..1..1..1..1....0..0..0..1....1..1..1..1....0..0..0..0....0..0..0..1

CROSSREFS

Column 3 of A253159.

Sequence in context: A045021 A254712 A197172 * A140368 A039434 A043257

Adjacent sequences:  A253151 A253152 A253153 * A253155 A253156 A253157

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 28 2014

STATUS

approved

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Last modified September 17 22:06 EDT 2021. Contains 347489 sequences. (Running on oeis4.)