OFFSET
1,2
COMMENTS
Sum_{d|n} (d/sigma(d)) >= 1 for all n >= 1.
FORMULA
a(p) = p + 1 for primes p.
EXAMPLE
Sum_{d|n} (d/sigma(d)) for n >= 1: 1, 5/3, 7/4, 47/21, 11/6, 35/12, 15/8, 97/35, 127/52, 55/18, 23/12, 47/12, 27/14, ...
For n=4; Sum_{d|4} (d/sigma(d)) = 1/sigma(1) + 2/sigma(2) + 4/sigma(4) = 1/1 + 2/3 + 4/7 = 47/21; a(4) = 21.
PROG
(Magma) [Denominator(&+[d / SumOfDivisors(d): d in Divisors(n)]): n in [1..100]]
(PARI) a(n) = denominator(sumdiv(n, d, d/sigma(d))); \\ Michel Marcus, Mar 03 2019
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Mar 03 2019
STATUS
approved