A250096 - OEIS

%I #9 Nov 18 2021 17:13:04

%S 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,

%T 28,29,90,31,2,33,68,35,12,37,76,39,20,41,126,43,44,15,92,47,12,7,20,

%U 51,52,53,12,55,28,57,116,59,90,61,124,21,2,65,198,67,68

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

%C All primes are in this sequence.

%H Colin Barker, <a href="/A250096/b250096.txt">Table of n, a(n) for n = 2..1000</a>

%e a(18) = 12 because the distinct prime factors of 18 are [2,3] and 2 / (1/2+1/3) = 12/5.

%t Table[Numerator[HarmonicMean[FactorInteger[n][[All,1]]]],{n,2,70}] (* _Harvey P. Dale_, Nov 18 2021 *)

%o (PARI)

%o harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])

%o a(n) = numerator(harmonicmean(factorint(n)~[1,]))

%o vector(100, n, a(n+1))

%Y Cf. A250097.

%K nonn

%O 2,1

%A _Colin Barker_, Nov 12 2014