OFFSET
1,2
COMMENTS
The unitary version of A033632.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
33 is the sequence since usigma(uphi(33)) = usigma(20) = 30 and uphi(usigma(33)) = uphi(48) = 30.
MATHEMATICA
usigma[1]=1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); uphi[1] = 1; uphi[n_] := Times @@ (-1 + Power @@@ FactorInteger[n]); aQ[n_] := usigma[uphi[n]] == uphi[usigma[n]]; Select[Range[22000], aQ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 19 2019
STATUS
approved