OFFSET
1,1
COMMENTS
The zero values are easy to prove because of the bounds on the phi function.
phi(15)=2*4, so a(4)=15.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
EXAMPLE
sigma(4)=7, 4 is the smallest, so a(7)=4.
PROG
(PARI) a(n)=n+=n; for(k=n+1, solve(x=n, if(n<20, 99, 5*n*log(log(n))), x/(exp(Euler)*log(log(x))+3/log(log(x)))-n), if(eulerphi(k)==n, return(k))); 0 \\ Charles R Greathouse IV, Dec 19 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved