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A225340 Number of nX4 -1,1 arrays such that the sum over i=1..n,j=1..4 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 4-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship) 1
1, 1, 3, 9, 31, 107, 395, 1525, 6095, 24893, 103583, 437763, 1874497, 8116459, 35485099, 156453779, 694956997, 3107415563, 13976787615, 63201012187, 287163163723, 1310481411725, 6004334305049, 27611237977705, 127399143883589 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Column 4 of A225345

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..135

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

CROSSREFS

Sequence in context: A148965 A130620 A202246 * A148966 A279971 A127927

Adjacent sequences:  A225337 A225338 A225339 * A225341 A225342 A225343

KEYWORD

nonn

AUTHOR

R. H. Hardin May 05 2013

STATUS

approved

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Last modified November 18 12:35 EST 2019. Contains 329261 sequences. (Running on oeis4.)