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A112813 Numbers k such that lcm(1,2,3,...,k)/3 equals the denominator of the k-th harmonic number H(k). 13
6, 7, 8, 18, 19, 25, 26, 54, 55, 56, 57, 58, 59, 60, 61, 62, 72, 73, 74, 75, 76, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
When 3 occurs in A110566.
LINKS
MATHEMATICA
f[n_] := LCM @@ Range[n]/Denominator[ HarmonicNumber[n]]; Select[ Range[231], f[ # ] == 3 &]
PROG
(PARI) isok(n) = lcm(vector(n, i, i)) == 3*denominator(sum(i=1, n, 1/i)); \\ Michel Marcus, Mar 07 2018
CROSSREFS
Sequence in context: A087663 A355199 A358557 * A347808 A048018 A254714
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Sep 17 2005
STATUS
approved

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Last modified May 26 14:41 EDT 2024. Contains 372826 sequences. (Running on oeis4.)