A225339 - OEIS

A225339

Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 3-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship)

0, 0, 0, 6, 0, 0, 0, 410, 0, 0, 0, 47990, 0, 0, 0, 7030132, 0, 0, 0, 1163743294, 0, 0, 0, 208310242542, 0, 0, 0, 39371238885750, 0, 0, 0, 7745062224896578, 0, 0, 0, 1571069270148096124, 0, 0, 0, 326518765865030556374, 0, 0, 0

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OFFSET

1,4

COMMENTS

Column 3 of A225345

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..159

EXAMPLE

All 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