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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). 12
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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Cf. A002805, A003418, A110566.

Cf. A098464, A112814, A112815, A112816, A112817, A112818, A112819, A112820, A112821, A112822.

Sequence in context: A155150 A078745 A087663 * A048018 A254714 A047197

Adjacent sequences:  A112810 A112811 A112812 * A112814 A112815 A112816

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Sep 17 2005

STATUS

approved

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Last modified July 30 04:49 EDT 2021. Contains 346348 sequences. (Running on oeis4.)