login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A060657 Sigma(x) has an odd solution n. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

That is, the odd values produced by the sigma function.

Odd terms of A002191. - Michel Marcus, Jun 10 2014

LINKS

Table of n, a(n) for n=1..52.

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: A080565 A164344 A002254 * A192148 A151875 A117533

Adjacent sequences:  A060654 A060655 A060656 * A060658 A060659 A060660

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 18 2001

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 20 21:06 EDT 2019. Contains 327247 sequences. (Running on oeis4.)