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 A015880 #31 Feb 10 2024 11:36:00 %S A015880 21,174,270,517,572,913,992,1002,1420,1633,1830,2622,2958,4170,4747, %T A015880 5539,7520,7544,7729,10184,10783,14863,16165,16520,19837,20935,21584, %U A015880 23161,26840,28544,29737,31453,34510,35571,35611,35845,39560 %N A015880 Numbers k such that sigma(k) = sigma(k+10). %H A015880 Donovan Johnson, <a href="/A015880/b015880.txt">Table of n, a(n) for n = 1..1000</a> %H A015880 A. Weingartner, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Weingartner/wein3.html">On the Solutions of sigma(n) = sigma(n+k)</a>, Journal of Integer Sequences, Vol. 14 (2011), #11.5.5. %t A015880 Select[Range[40000], DivisorSigma[1, #]==DivisorSigma[1, # + 10] &] (* _Vincenzo Librandi_, Mar 10 2014 *) %o A015880 (PARI) is(n)=sigma(n)==sigma(n+10) \\ _Charles R Greathouse IV_, Mar 09 2014 %Y A015880 Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015881, A015882, A015883, A181647. %K A015880 nonn %O A015880 1,1 %A A015880 _Robert G. Wilson v_