This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A015861 #30 Dec 01 2024 11:01:40
%S A015861 382,8922,11935,31815,32442,61982,123795,145915,186615,271215,442362,
%T A015861 554715,560382,580635,964535,1191575,1243375,1369302,1539942,1642795,
%U A015861 2616702,3141215,3299062,3556035,3716895,4201015,5148294
%N A015861 Numbers k such that sigma(k) = sigma(k+3).
%H A015861 Donovan Johnson, <a href="/A015861/b015861.txt">Table of n, a(n) for n = 1..300</a>
%t A015861 Flatten[Position[Partition[DivisorSigma[1,Range[5200000]],4,1],{x_, y_, z_, x_}]] (* _Harvey P. Dale_, Aug 08 2011 *)
%t A015861 Select[Range[6000000], DivisorSigma[1, #]==DivisorSigma[1, # + 3] &] (* _Vincenzo Librandi_, Mar 10 2014 *)
%t A015861 SequencePosition[DivisorSigma[1,Range[5150000]],{x_,_,_,x_}][[;;,1]] (* _Harvey P. Dale_, Dec 01 2024 *)
%o A015861 (PARI) is(n)=sigma(n)==sigma(n+3) \\ _Charles R Greathouse IV_, Mar 09 2014
%Y A015861 Cf. A002961, A007373, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883, A181647.
%K A015861 nonn
%O A015861 1,1
%A A015861 _Robert G. Wilson v_