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A211578
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Number of -2..2 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having three, four, five or six distinct values for every i,j,k<=n.
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1
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16, 52, 144, 380, 964, 2456, 6124, 15508, 38608, 97780, 243828, 618200, 1544572, 3919940, 9810928, 24918052, 62460100, 158735704, 398435148, 1013116820, 2546214544, 6477456788, 16299033172, 41482468312, 104500505308, 266074661668
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) + 12*a(n-2) - 21*a(n-3) - 48*a(n-4) + 64*a(n-5) + 80*a(n-6) - 60*a(n-7) - 48*a(n-8).
Empirical g.f.: 4*x*(4 + 5*x - 38*x^2 - 49*x^3 + 84*x^4 + 116*x^5 - 18*x^6 - 36*x^7) / ((1 - x - x^2)*(1 - 2*x^2)*(1 - x - 4*x^2)*(1 - 6*x^2)). - Colin Barker, Jul 19 2018
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EXAMPLE
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Some solutions for n=5:
..0....2...-1....0....0....0....1...-2....1....1....1....2....2....2...-1....0
.-1....1....0....2...-2....2...-2...-1...-2....0....2....0....1....1...-2...-1
..0...-2....2....0...-1....0...-1...-2....1...-1...-1...-1...-2....2....1....0
.-1....1....0...-1....0....1....0...-1....0...-2....2....0...-1....0....2....1
..2...-2....2....0....1....2....1...-2...-1....0....1....2....0....2...-1....0
.-1....1....0....1....2....1....0...-1....2...-1...-2....1....1....0....2...-2
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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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