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URL: https://oeis.org/A113571

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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
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?)
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
Sequence in context: A145019 A066678 A306645 * A119018 A264647 A094748
KEYWORD
nonn
AUTHOR
EXTENSIONS
Entry revised (better definition, corrections, more terms) by Don Reble, Aug 14 2014
STATUS
approved