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A098464
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Numbers k such that lcm(1,2,3,...,k) equals the denominator of the k-th harmonic number H(k).
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18
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1, 2, 3, 4, 5, 9, 10, 11, 12, 13, 14, 15, 16, 17, 27, 28, 29, 30, 31, 32, 49, 50, 51, 52, 53, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149
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OFFSET
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1,2
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COMMENTS
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Numbers k such that A110566(k) = 1.
Shiu (2016) conjectured that this sequence is infinite. - Amiram Eldar, Feb 02 2021
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LINKS
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MATHEMATICA
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Select[Range[250], LCM@@Range[ # ]==Denominator[HarmonicNumber[ # ]]&]
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PROG
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(PARI) isok(n) = lcm(vector(n, i, i)) == denominator(sum(i=1, n, 1/i)); \\ Michel Marcus, Mar 07 2018
(Python)
from fractions import Fraction
from sympy import lcm
k, l, h, A098464_list = 1, 1, Fraction(1, 1), []
while k < 10**6:
if l == h.denominator:
k += 1
l = lcm(l, k)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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