A015876 Numbers k such that sigma(k) = sigma(k+8).

15, 69, 87, 102, 132, 175, 230, 638, 689, 1127, 1349, 1392, 2006, 5170, 6680, 8366, 8390, 11652, 11918, 12128, 16748, 19511, 19829, 23318, 24597, 24734, 25122, 27162, 28676, 30730, 32864, 37391, 37436, 37901, 41082, 45925, 47487

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000
• A. Weingartner, On the Solutions of sigma(n) = sigma(n+k), Journal of Integer Sequences, Vol. 14 (2011), #11.5.5.

Crossrefs

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015877, A015880, A015881, A015882, A015883, A181647.

Programs

Mathematica

Select[Range[50000], DivisorSigma[1, #]==DivisorSigma[1, # + 8] &] (* Vincenzo Librandi, Mar 10 2014 *)

PARI

is(n)=sigma(n)==sigma(n+8) \\ Charles R Greathouse IV, Mar 09 2014