A225342 - OEIS

A225342

Number of nX6 -1,1 arrays such that the sum over i=1..n,j=1..6 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 6-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship)

1, 1, 3, 17, 81, 397, 2073, 11291, 63121, 360909, 2102597, 12439855, 74561687, 451920441, 2765717847, 17069622035, 106139191511, 664358517275, 4183117802521, 26479526009223, 168426949915891, 1076002461947039

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OFFSET

1,3

COMMENTS

Column 6 of A225345

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..112

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