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A113571 Let H(n) be the reduced fraction Sum_{i=1..n} 1/i. a(n) is the least factor of H(n)'s numerator or denominator that doesn't divide either part of any earlier H(m). 0
1, 2, 6, 4, 10, 7, 14, 8, 9, 61, 22, 13, 26, 1049, 41233, 16, 34, 19, 38, 11167027, 18858053, 23, 46, 138, 50, 34395742267, 27, 841, 58, 31, 62, 32, 269, 3583, 397, 1297, 74, 199, 737281, 41, 82, 301, 86, 407, 1553, 47, 94, 2323031, 98, 587948341, 76943, 2809, 106, 5953, 51862596437, 252476961434436524654789, 26693, 59, 118, 2207, 122, 928551009361054917576341971, 347, 64, 2473, 67, 134 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also, a(n) is the first occurrence of n in A110545.

Conjectured last occurrence of n: 1,3,11,25,137,49,363,761,7129,7381,83711, [sic] 6617,72072,1117 (is this A001008?)

LINKS

Table of n, a(n) for n=1..67.

MATHEMATICA

f[n_] := f[n] = Block[{h = k = 1}, While[ !IntegerQ[ Numerator[h]/n] && ! IntegerQ[Denominator[h]/n], k++; h = h + 1/k]; k]; Do[ f[n], {n, 84000}]; Table[ Select[ Range[84000], f[ # ] == n &][[1]], {n, 60}]

CROSSREFS

Cf. A110545, A001008.

Sequence in context: A238642 A145019 A066678 * A119018 A264647 A094748

Adjacent sequences:  A113568 A113569 A113570 * A113572 A113573 A113574

KEYWORD

nonn

AUTHOR

Leroy Quet and Robert G. Wilson v, Sep 29 2005

EXTENSIONS

Entry revised (better definition, corrections, more terms) by Don Reble, Aug 14 2014

STATUS

approved

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Last modified February 21 22:56 EST 2018. Contains 299427 sequences. (Running on oeis4.)