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Numbers k such that sigma(k) + 6 = sigma(k+6).
10

%I #20 Jul 04 2021 00:30:35

%S 5,7,11,13,17,23,31,37,41,47,53,61,67,73,83,97,101,103,104,107,131,

%T 147,151,157,167,173,191,193,223,227,233,251,257,263,271,277,307,311,

%U 331,347,353,367,373,383,433,443,457,461,503,541,557,563,571

%N Numbers k such that sigma(k) + 6 = sigma(k+6).

%H Reinhard Zumkeller, <a href="/A015914/b015914.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[50000], DivisorSigma[1, #] + 6==DivisorSigma[1, # + 6] &] (* _Vincenzo Librandi_, Mar 10 2014 *)

%Y Cf. A000203.

%Y See A054903 for nonprimes. - _Reinhard Zumkeller_, Jan 27 2009

%K nonn

%O 1,1

%A _Robert G. Wilson v_