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A213121
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Number of binary arrays of length 2*n+3 with fewer than n ones in any length 2n subsequence (=less than 50% duty cycle).
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1
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1, 14, 86, 424, 1926, 8404, 35836, 150604, 626726, 2589844, 10646676, 43594464, 177950236, 724578824, 2944375096, 11944652884, 48388816486, 195794585044, 791434666276, 3196307541904, 12898839944116, 52019043912664
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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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Recurrence: n*(7*n-19)*a(n) = 2*(28*n^2-97*n+60)*a(n-1) - 8*(2*n-5)*(7*n-12) * a(n-2). - Vaclav Kotesovec, Oct 19 2012
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EXAMPLE
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Some solutions for n=3
..0....0....1....0....0....0....0....0....0....0....1....1....1....1....0....1
..0....0....0....0....0....1....0....1....1....0....1....0....0....0....0....0
..1....1....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....1....0....0....0....1....0....1....0....0....0....0....0....1
..1....0....1....0....1....1....0....0....1....1....0....0....0....0....0....0
..0....0....0....0....1....0....0....0....0....0....0....0....1....0....0....0
..0....0....0....0....0....0....0....0....0....0....1....0....0....1....0....0
..0....1....0....1....0....0....0....0....0....0....0....1....1....0....1....0
..0....1....1....0....0....1....0....0....0....0....0....1....0....0....1....0
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MATHEMATICA
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Table[2^(2*n+2)-5*(7*n-4)*Binomial[2*n-2, n-1]/n, {n, 1, 20}] (* Vaclav Kotesovec, Oct 29 2012 *)
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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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