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A225304 Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero and rows are nondecreasing (ways to put 3 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate) 1
0, 0, 6, 16, 0, 0, 474, 1576, 0, 0, 64700, 228876, 0, 0, 10659862, 38869960, 0, 0, 1941920508, 7211917300, 0, 0, 376790653888, 1416598649968, 0, 0, 76344225166632, 289560610889154, 0, 0, 15965033749025502, 60953934482465398, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Column 3 of A225310
LINKS
EXAMPLE
Some solutions for n=4
.-1.-1..1...-1.-1.-1....1..1..1...-1.-1.-1...-1.-1..1...-1.-1.-1...-1..1..1
.-1.-1.-1...-1..1..1...-1.-1.-1....1..1..1....1..1..1...-1.-1.-1...-1..1..1
.-1..1..1...-1.-1..1...-1.-1.-1....1..1..1...-1.-1.-1...-1.-1..1....1..1..1
.-1..1..1...-1..1..1....1..1..1...-1.-1.-1...-1..1..1....1..1..1...-1.-1.-1
CROSSREFS
Sequence in context: A280964 A191463 A235943 * A299709 A107777 A136140
KEYWORD
nonn
AUTHOR
R. H. Hardin May 05 2013
STATUS
approved

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Last modified March 3 07:49 EST 2024. Contains 370499 sequences. (Running on oeis4.)