A015916 - OEIS

%I #23 Jul 03 2021 19:52:53

%S 3,7,13,19,31,37,43,61,73,79,97,103,127,139,157,163,181,223,229,241,

%T 271,283,307,337,349,373,379,409,421,433,439,457,499,547,577,607,631,

%U 643,673,691,709,733,751,787,811,829,853,877,919,937,967,1009

%N Numbers k such that sigma(k) + 10 = sigma(k+10).

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

%H Vincenzo Librandi, <a href="/A015916/b015916.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[2000], DivisorSigma[1, #] + 10==DivisorSigma[1, # + 10] &] (* _Vincenzo Librandi_, Mar 10 2014 *)

%t Select[Partition[DivisorSigma[1,Range[1100]],11,1],#[[1]]+10==#[[-1]]&][[All,1]]-1 (* _Harvey P. Dale_, May 20 2021 *)

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

%K nonn

%O 1,1

%A _Robert G. Wilson v_