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
KEYWORD
nonn
AUTHOR
Colin Barker, Nov 12 2014
STATUS
approved