A175876 Numbers k such that sigma(k+2) = 2*sigma(k).

118, 1558, 2938, 17758, 19918, 32218, 33838, 55963, 71038, 186778, 308038, 511498, 523774, 553498, 699358, 838213, 1048903, 1159378, 1328938, 1333246, 1700038, 2462686, 2703886, 2956078, 3115318, 3561094, 3764206, 3972694, 7625878, 7852918, 8048962

Offset

1,1

Comments

a(1) = A175874(2).

Links

Vincenzo Librandi and Donovan Johnson, Table of n, a(n) for n = 1..1000 (first 171 terms from Vincenzo Librandi)

Mathematica

Do[If[DivisorSigma[1, n+2]==2 DivisorSigma[1, n], Print[n]], {n, 2, 10^7}] (* or *) Select[Range[8000000], DivisorSigma[1, # + 2] == 2 DivisorSigma[1, #]&](* Vincenzo Librandi, Apr 04 2013 *)

Crossrefs

Cf. A000203, A002961, A175874, A175875.

Sequence in context: A250793 A334646 A232776 * A220715 A230917 A230248

Adjacent sequences: A175873 A175874 A175875 * A175877 A175878 A175879

Keyword

nonn

Author

Zak Seidov, Oct 06 2010

Status

approved