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A225343 Number of nX7 -1,1 arrays such that the sum over i=1..n,j=1..7 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 7-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship) 1

%I #4 May 05 2013 14:38:59

%S 0,0,0,22,0,0,0,25056,0,0,0,47084448,0,0,0,110202390974,0,0,0,

%T 291612344834026,0,0,0,834664320724959518,0,0,0,

%U 2522954614267660110474,0,0,0,7938386813443913197221460,0,0,0,25757964315025150183357153902,0,0,0

%N Number of nX7 -1,1 arrays such that the sum over i=1..n,j=1..7 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 7-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship)

%C Column 7 of A225345

%H R. H. Hardin, <a href="/A225343/b225343.txt">Table of n, a(n) for n = 1..105</a>

%e Some solutions for n=4

%e .-1.-1.-1.-1..1..1..1...-1.-1..1..1..1..1..1...-1.-1.-1.-1.-1..1..1

%e .-1.-1.-1..1..1..1..1...-1.-1.-1.-1.-1..1..1...-1..1..1..1..1..1..1

%e .-1.-1.-1..1..1..1..1...-1.-1.-1.-1.-1..1..1...-1.-1.-1.-1..1..1..1

%e .-1.-1.-1.-1..1..1..1...-1.-1..1..1..1..1..1...-1.-1.-1.-1..1..1..1

%K nonn

%O 1,4

%A _R. H. Hardin_ May 05 2013

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Last modified April 25 03:15 EDT 2024. Contains 371964 sequences. (Running on oeis4.)