OFFSET
1,1
COMMENTS
a(5) > 10^10. - Giovanni Resta, Oct 14 2013
EXAMPLE
Arithmetic derivative of 15 is 8 and sigma(8) = 15.
MAPLE
with(numtheory); P:=proc(q) local n; for n from 1 to q do
if n=sigma(n*add(op(2, p)/op(1, p), p=ifactors(n)[2])) then print(n);
fi; od; end: P(10^9);
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Oct 14 2013
STATUS
approved