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A253449 Number of (n+1) X (1+1) 0..2 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally and vertically. 2
81, 414, 1388, 3639, 8501, 19701, 48293, 126357, 346997, 982677, 2837237, 8295957, 24462197, 72541077, 215938037, 644449557, 1926625397, 5766435477, 17272430837, 51763547157, 155183156597, 465334505877, 1395573595637, 4185860948757 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A253456.

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>10.

Empirical: a(n) = 400*3^(n-3) + 205*2^(n-1) + 2917 for n>7.

Empirical g.f.: x*(81 - 72*x - 205*x^2 - 621*x^3 - 549*x^4 + 396*x^5 + 1764*x^6 + 2304*x^7 + 1872*x^8 + 864*x^9) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Mar 20 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Cf. A253456.

Sequence in context: A253495 A253456 A236155 * A236148 A205986 A206668

Adjacent sequences:  A253446 A253447 A253448 * A253450 A253451 A253452

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 01 2015

STATUS

approved

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Last modified July 24 14:51 EDT 2021. Contains 346273 sequences. (Running on oeis4.)