OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
a(p) = p, for p prime.
MATHEMATICA
uphi[n_] := Product[{p, e} = pe; p^e - 1, {pe, FactorInteger[n]}];
a[n_] := Denominator[uphi[n]/n];
Array[a, 100] (* Jean-François Alcover, Jan 10 2022 *)
PROG
(PARI) a(n)=my(f=factor(n)~); denominator(prod(i=1, #f, f[1, i]^f[2, i]-1)/n);
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Michel Marcus, Sep 26 2018
STATUS
approved