login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A162280 Second numbers with the same values for sigma_0(n) and sigma(n) as one or more other numbers. 4
15, 35, 51, 69, 95, 56, 115, 70, 143, 145, 155, 159, 110, 177, 135, 205, 235, 154, 265, 287, 195, 140, 295, 184, 329, 231, 335, 377, 355, 238, 325, 339, 413, 266, 415, 286, 220, 473, 445, 497, 310, 533, 447, 589, 583, 374, 501, 455, 308, 565, 537, 376, 270 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that for exactly one m < n, sigma(n) = sigma(m) and sigma_0(n) = sigma_0(m). There may be more such m > n.

The associated m values are in A162279.

See the a-file for a PARI program and more values.

LINKS

Table of n, a(n) for n=1..53.

Franklin T. Adams-Watters, Table of duplicate sigma values up to sigma(n) = 10000

EXAMPLE

sigma(14) = sigma(15) = 24, sigma_0(14) = sigma_0(15) = 4, so 15 is in the sequence. sigma(16) = sigma(25) = 31, but sigma_0(16) = 5 != sigma_0(25) = 3, so 25 is not in the sequence

CROSSREFS

Cf. A000005, A000203, A162279, A162281, A162282, A162283.

Sequence in context: A108668 A201018 A187400 * A290781 A063532 A212331

Adjacent sequences:  A162277 A162278 A162279 * A162281 A162282 A162283

KEYWORD

nonn

AUTHOR

Franklin T. Adams-Watters, Jun 29 2009

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 January 21 13:47 EST 2020. Contains 331113 sequences. (Running on oeis4.)