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A253496 Number of (2+1) X (n+1) 0..2 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally, vertically and ne-to-sw antidiagonally. 1
414, 1377, 3090, 5386, 9679, 20975, 51167, 133311, 362399, 1014975, 2903327, 8429631, 24731039, 73080255, 217017887, 646610751, 1930949279, 5775084735, 17289730847, 51798148671, 155252361119, 465472916415, 1395850418207 (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) = 400*3^(n-3) + 271*2^(n-1) + 1423 for n>6.

Empirical g.f.: x*(414 - 1107*x - 618*x^2 - 491*x^3 + 3091*x^4 + 3607*x^5 - 530*x^6 - 1040*x^7 - 480*x^8) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Dec 16 2018

EXAMPLE

Some solutions for n=4:

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

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

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

CROSSREFS

Row 2 of A253495.

Sequence in context: A027661 A260472 A253489 * A253450 A236149 A231312

Adjacent sequences:  A253493 A253494 A253495 * A253497 A253498 A253499

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 02 2015

STATUS

approved

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Last modified October 21 16:50 EDT 2019. Contains 328302 sequences. (Running on oeis4.)