OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..569
EXAMPLE
6 is a term since its even divisors are 2 and 6, and their harmonic mean, 1/((1/2 + 1/6)/2) = 3, is an integer.
MATHEMATICA
Select[Range[2, 10^5, 2], IntegerQ[HarmonicMean[Select[Divisors[#], EvenQ]]] &]
PROG
(Python)
from sympy import gcd, divisor_sigma
A348412_list = [2*n for n in range(1, 10**3) if (lambda x, y: 2*gcd(x, y*n)>=x)(divisor_sigma(n), divisor_sigma(n, 0))] # Chai Wah Wu, Oct 20 2021
(PARI) isok(m) = if (! (m%2), my(d=select(x->!(x%2), divisors(m))); denominator(#d/sum(k=1, #d, 1/d[k])) == 1); \\ Michel Marcus, Oct 31 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 17 2021
STATUS
approved