OFFSET
1,2
FORMULA
a(n) = n * Sum_{d|n, tau(d)|d, gcd(d,n/d)=1} 1 / d.
MATHEMATICA
a[n_] := n*DivisorSum[n, 1/# &, CoprimeQ[#, n/#] && Divisible[#, DivisorSigma[0, #]] &]; Array[a, 100]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, May 27 2023
STATUS
approved