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A060657
Odd values of the sum-of-divisors function sigma (A000203) (without repetitions).
4
1, 3, 7, 13, 15, 31, 39, 57, 63, 91, 93, 121, 127, 133, 171, 183, 195, 217, 255, 307, 363, 381, 399, 403, 465, 511, 549, 553, 741, 781, 819, 847, 855, 871, 921, 931, 961, 993, 1023, 1093, 1143, 1209, 1281, 1407, 1651, 1659, 1723, 1729, 1767, 1815, 1893, 1953
OFFSET
1,2
COMMENTS
That is, the odd values produced by the sigma function.
Odd terms of A002191. - Michel Marcus, Jun 10 2014
LINKS
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
Cf. A007369.
Sequence in context: A002254 A356211 A331036 * A192148 A151875 A117533
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 18 2001
EXTENSIONS
Name edited by Giovanni Resta, Jan 08 2020
STATUS
approved