OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..92
EXAMPLE
The first 5 in the sequence corresponds to n = 92; indeed, (sigma(sigma(92))-phi(phi(92)))/92 = (sigma(168)-phi(44))/92 = (480-20)/92 = 5.
MAPLE
with(numtheory): a:=proc(n) if type((sigma(sigma(n))-phi(phi(n)))/n, integer) =true then (sigma(sigma(n))-phi(phi(n)))/n else end if end proc: seq(a(n), n= 1..1000000);
PROG
(PARI) { for(n=1, 10000000, my(ss=sigma(sigma(n))-eulerphi(eulerphi(n))); if(ss%n==0, print1(ss/n, ", ") ; ) ; ) ; } \\ R. J. Mathar, Mar 07 2008
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Mar 03 2008
EXTENSIONS
More terms from R. J. Mathar, Mar 07 2008
STATUS
approved