OFFSET
1,2
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
6 is a term since usigma(6) = 12 is divisible by uphi(6) = 2.
MATHEMATICA
f[1, 1] = 1; f[p_, e_]:= (p^e + 1)/(p^e -1); ubalQ[n_] := IntegerQ[Times @@ (f @@@ FactorInteger[n])]; Select[Range[10^4], ubalQ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, May 30 2020
STATUS
approved