A250096 Numerator of the harmonic mean of the prime factors, without multiplicity, of n.

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

Colin Barker, Table of n, a(n) for n = 2..1000

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

Adjacent sequences: A250093 A250094 A250095 * A250097 A250098 A250099

Keyword

nonn

Author

Colin Barker, Nov 12 2014

Status

approved