OFFSET
1,1
COMMENTS
a(5) > 45*10^9. - Giovanni Resta, Sep 05 2017
EXAMPLE
52298 is a term because phi(sigma(52298) - 52298) = phi(27382) = 13690, sigma(phi(52298)) - phi(52298) = sigma(25740) - 25740 = 65988 and 65988 - 13690 = 52298.
PROG
(PARI) a001615(n) = sigma(n)-n;
isok(n) = a001615(eulerphi(n))==n+eulerphi(a001615(n));
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Sep 04 2017
EXTENSIONS
a(4) from Giovanni Resta, Sep 05 2017
STATUS
approved