login
A250096
Numerator of the harmonic mean of the prime factors, without multiplicity, of n.
2
2, 3, 2, 5, 12, 7, 2, 3, 20, 11, 12, 13, 28, 15, 2, 17, 12, 19, 20, 21, 44, 23, 12, 5, 52, 3, 28, 29, 90, 31, 2, 33, 68, 35, 12, 37, 76, 39, 20, 41, 126, 43, 44, 15, 92, 47, 12, 7, 20, 51, 52, 53, 12, 55, 28, 57, 116, 59, 90, 61, 124, 21, 2, 65, 198, 67, 68
OFFSET
2,1
COMMENTS
All primes are in this sequence.
LINKS
EXAMPLE
a(18) = 12 because the distinct prime factors of 18 are [2,3] and 2 / (1/2+1/3) = 12/5.
MATHEMATICA
Table[Numerator[HarmonicMean[FactorInteger[n][[All, 1]]]], {n, 2, 70}] (* Harvey P. Dale, Nov 18 2021 *)
PROG
(PARI)
harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
a(n) = numerator(harmonicmean(factorint(n)~[1, ]))
vector(100, n, a(n+1))
CROSSREFS
Cf. A250097.
Sequence in context: A183101 A343300 A285309 * A345302 A357183 A350177
KEYWORD
nonn
AUTHOR
Colin Barker, Nov 12 2014
STATUS
approved