|
%I #26 Jul 04 2021 00:14:44
%S 3,7,13,19,37,43,67,79,97,103,109,127,163,193,223,229,277,307,313,349,
%T 379,397,439,457,463,487,499,613,643,673,739,757,769,823,853,859,877,
%U 883,907,937,967,1009,1087,1093,1213,1279,1297,1303,1423
%N Numbers k such that sigma(k) + 4 = sigma(k+4).
%C This sequence contains the composite number 305635357, so is different from A023200 and A029710 (305635357 is the only composite member of the present sequence below 10^9). - _Jud McCranie_, Jan 07 2001
%H Vincenzo Librandi, <a href="/A015913/b015913.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[Range[1500],DivisorSigma[1,#]+4==DivisorSigma[1,#+4]&] (* _Harvey P. Dale_, Nov 04 2011 *)
%o (PARI) is(n)=sigma(n)+4==sigma(n+4) \\ _Charles R Greathouse IV_, Mar 09 2014
%Y Cf. A023200, A029710.
%K nonn
%O 1,1
%A _Robert G. Wilson v_
|
