OFFSET
1,1
COMMENTS
It is conjectured that there are no other solutions.
This sequence is finite, since by Grönwall's theorem sigma_4(n) <= sigma(n)^4 << (n log log n)^4 but phi(n)^5 >> (n/log log n)^5. - Charles R Greathouse IV, Nov 19 2015
FORMULA
Solutions to A001159(n) > phi(n)^5.
MATHEMATICA
Select[Range[2400], DivisorSigma[4, #]>EulerPhi[#]^5&] (* Harvey P. Dale, Aug 20 2021 *)
PROG
(PARI) is(n)=my(f=factor(n)); sigma(f, 4)>eulerphi(f)^5 \\ Charles R Greathouse IV, Nov 19 2015
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Labos Elemer, Sep 27 2001
STATUS
approved