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A225313
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Number of 6Xn -1,1 arrays such that the sum over i=1..6,j=1..n of i*x(i,j) is zero and rows are nondecreasing (ways to put n thrusters pointing east or west at each of 6 positions 1..n distance from the hinge of a south-pointing gate without turning the gate)
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1
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0, 35, 0, 443, 0, 2341, 0, 8221, 0, 22351, 0, 51521, 0, 105247, 0, 196779, 0, 342979, 0, 565693, 0, 891247, 0, 1352233, 0, 1986519, 0, 2839617, 0, 3963039, 0, 5417341, 0, 7269805, 0, 9598181, 0, 12487593, 0, 16035169, 0, 20345971, 0, 25538619, 0
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = a(n-2) +a(n-4) -a(n-10) -2*a(n-14) +a(n-18) +a(n-20) +a(n-22) +a(n-24) -2*a(n-28) -a(n-32) +a(n-38) +a(n-40) -a(n-42)
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EXAMPLE
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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...-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
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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