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 A058072 #33 Feb 19 2024 10:29:29 %S A058072 1,5,14,125,206,957,1253,1334,1364,1634,1673,1919,2685,2759,2974,3127, %T A058072 4364,5191,7615,11219,12035,14841,18873,19358,20145,24957,27089,33998, %U A058072 36566,42818,43817,47795,48559,49955,50039,56564,56975,58373,58463 %N A058072 Numbers k such that sigma(k) divides sigma(k+1), where sigma(k) is sum of positive divisors of k. %C A058072 The quotient (sigma(k+1)/sigma(k)) is equal to 1, 2, 3, 4 or 5 for the first 5000 terms. - _Donovan Johnson_, Oct 21 2012 %H A058072 Donovan Johnson, <a href="/A058072/b058072.txt">Table of n, a(n) for n = 1..5000</a> %e A058072 5 is included because sigma(5) = 6 divides sigma(6) = 12. %t A058072 Select[Range[10^5], Divisible[DivisorSigma[1, # + 1], DivisorSigma[1, #]] &] (* _Michael De Vlieger_, Sep 03 2017 *) %o A058072 (PARI) isok(n) = !(sigma(n+1) % sigma(n)); \\ _Michel Marcus_, Sep 04 2017 %Y A058072 Cf. A000203, A002961. %K A058072 nonn %O A058072 1,2 %A A058072 _Leroy Quet_, Nov 11 2000 %E A058072 More terms from _Benoit Cloitre_, Jul 27 2002