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A253451 Number of (n+1) X (3+1) 0..2 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally and vertically. 1
1388, 4782, 7782, 11147, 19254, 39463, 89556, 218326, 561564, 1505134, 4163556, 11794246, 33997164, 99227614, 292162356, 865453366, 2574299964, 7678786894, 22948141956, 68667995686, 205651133964, 616247702974, 1847331718356 (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) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) for n>9.

Empirical: a(n) = 529*3^(n-3) + 673*2^(n-1) + 3635 for n>6.

Empirical g.f.: x*(1388 - 3546*x - 5642*x^2 + 8729*x^3 + 9282*x^4 - 136*x^5 - 2310*x^6 - 441*x^7 - 54*x^8) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Dec 13 2018

EXAMPLE

Some solutions for n=4:

..0..1..1..0....1..2..2..0....1..0..1..2....0..2..2..2....1..2..2..2

..1..1..1..0....2..2..2..0....2..0..0..0....1..2..1..0....2..2..2..2

..2..1..1..0....2..2..2..0....2..0..0..0....1..2..1..1....1..1..1..1

..2..1..1..1....2..2..2..0....2..0..0..0....0..1..0..1....2..2..2..2

..1..0..0..1....0..0..0..1....2..0..0..2....0..1..0..2....0..0..0..0

CROSSREFS

Column 3 of A253456.

Sequence in context: A259722 A253497 A253490 * A281164 A250816 A031983

Adjacent sequences:  A253448 A253449 A253450 * A253452 A253453 A253454

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 01 2015

STATUS

approved

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Last modified August 5 16:48 EDT 2021. Contains 346486 sequences. (Running on oeis4.)