OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..92 (terms < 10^10)
EXAMPLE
n = 92 is in the sequence because sigma(sigma(92))-phi(phi(92)) = sigma(168)-phi(44) = 480-20 = 460 = 5*92.
MAPLE
with(numtheory): a:=proc(n) if type((sigma(sigma(n))-phi(phi(n)))/n, integer) =true then n else end if end proc: seq(a(n), n=1..100000);
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Mar 03 2008
STATUS
approved