A162280 Second numbers with the same values for sigma_0(n) and sigma(n) as one or more other numbers.

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

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 A340449 A063532

Adjacent sequences: A162277 A162278 A162279 * A162281 A162282 A162283

Keyword

nonn

Author

Franklin T. Adams-Watters, Jun 29 2009

Status

approved