OFFSET
1,2
COMMENTS
The graph supports the conjecture that all numbers except 2 appear only a finite number of times. Sequences A000396, A005820, A027687, A046060 and A046061 give the n for which the abundancy sigma(n)/n is 2, 3, 4, 5 and 6, respectively. See A134639 for the number of n having abundancy greater than 2. - T. D. Noe, Nov 04 2007
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1600 (using Flammenkamp's data)
Achim Flammenkamp, The Multiply Perfect Numbers Page
Eric Weisstein's World of Mathematics, Abundancy
MAPLE
with(numtheory): for i while i < 33000 do
if sigma(i) mod i = 0 then print(sigma(i)/i) fi od;
PROG
(PARI) for(n=1, 1e7, if(denominator(k=sigma(n, -1))==1, print1(k", "))) \\ Charles R Greathouse IV, Mar 09 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Asher Auel, Jan 19 2000
EXTENSIONS
More terms from Jud McCranie, Jul 09 2000
More terms from David Wasserman, Jun 28 2004
STATUS
approved