A015916 Numbers k such that sigma(k) + 10 = sigma(k+10).

3, 7, 13, 19, 31, 37, 43, 61, 73, 79, 97, 103, 127, 139, 157, 163, 181, 223, 229, 241, 271, 283, 307, 337, 349, 373, 379, 409, 421, 433, 439, 457, 499, 547, 577, 607, 631, 643, 673, 691, 709, 733, 751, 787, 811, 829, 853, 877, 919, 937, 967, 1009

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Comments

Different from A023203. Below 1000000 the only composite number here is 195556: sigma(195556) + 10 = 342230 + 10 = sigma(195566). - Labos Elemer, May 23 2000

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A023203, A015913, A015914, A015915, A015917.

Programs

Mathematica

Select[Range[2000], DivisorSigma[1, #] + 10==DivisorSigma[1, # + 10] &] (* Vincenzo Librandi, Mar 10 2014 *)
Select[Partition[DivisorSigma[1,Range[1100]],11,1],#[[1]]+10==#[[-1]]&][[All,1]]-1 (* Harvey P. Dale, May 20 2021 *)