A015883 Numbers k such that sigma(k) = sigma(k+13).

182, 782, 1965, 2486, 2678, 2685, 12141, 12441, 17342, 21242, 27686, 34905, 35505, 35853, 38662, 38985, 56732, 63578, 104342, 109461, 192933, 198909, 222122, 236966, 245349, 251654, 256322, 261885, 262238, 324441, 333909

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

References

• J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 182, p. 56, Ellipses, Paris 2008.

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A181647.

Programs

Mathematica

Select[Range[350000], DivisorSigma[1, #]==DivisorSigma[1, # + 13] &] (* Vincenzo Librandi, Mar 10 2014 *)

PARI

is(n)=sigma(n)==sigma(n+13) \\ Charles R Greathouse IV, Mar 09 2014

Extensions

Corrected by T. D. Noe, Oct 31 2006