OFFSET
1,2
COMMENTS
No further term below 10^7.
a(25) > 5*10^10. - Donovan Johnson, Jul 26 2011
EXAMPLE
sigma(1) - sigma(2) = -2, which is divisible by 2, so 2 is a term of the sequence.
MATHEMATICA
s = 0; Do[s = s + (-1)^(i + 1) * DivisorSigma[1, i]; If[Mod[s, i] == 0, Print[i]], {i, 1, 10^5}]
PROG
(PARI) {a067931(m)=local(s, n); s=0; for(n=1, m, if(n%2==0, s=s-sigma(n), s=s+sigma(n)); if(s%n==0, print1(n, ", ")))}
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Joseph L. Pe, Feb 22 2002
EXTENSIONS
Edited and extended by Klaus Brockhaus, Feb 28 2002
a(19)-a(24) from Donovan Johnson, Jul 26 2011
STATUS
approved