OFFSET
1,2
COMMENTS
That is, the odd values produced by the sigma function.
Odd terms of A002191. - Michel Marcus, Jun 10 2014
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
EXAMPLE
a(7) = 39 because sigma(18) = 1+2+3+6+9+18 = 39, an odd number.
MATHEMATICA
nn = 2000; Union[Select[DivisorSigma[1, Range[nn]], OddQ[#] && # <= nn &]] (* Harvey P. Dale, Mar 12 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 18 2001
EXTENSIONS
Name edited by Giovanni Resta, Jan 08 2020
STATUS
approved