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A232090
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Minimal possible denominator for a sum of the form 1 +/- 1/2 +/- 1/3 +/- ... +/- 1/n.
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3
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1, 2, 6, 12, 60, 20, 140, 280, 2520, 2520, 27720, 27720, 360360, 360360, 72072, 144144, 2450448, 272272, 5173168, 5173168, 739024, 739024, 16997552, 16997552, 424938800, 424938800, 11473347600, 11473347600, 332727080400, 332727080400
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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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MATHEMATICA
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nMax = 19; d = {0}; Table[d = Flatten[{d + 1/n, d - 1/n}]; Min[Denominator[d]], {n, nMax}] (* T. D. Noe, Nov 19 2013 *)
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PROG
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(PARI) for(n=0, 19, m=(n+1)!; for(k=0, 2^n-1, m=min(denominator(sum(j=2, n+1, (-1)^bittest(k, j-2)/j, 1)), m)); print1(m", "))
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CROSSREFS
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Cf. A061195 (minimal possible positive numerator).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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