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 A015891 #15 Oct 23 2018 05:46:19 %S A015891 1,2,5,6,10,30,70,1565,2806,3126,51670,58290,214405,285286,378258, %T A015891 1854766,2170486,2222122,2247610,3463230,4147522,5942526,9381126, %U A015891 14818486,15743890,20162858,34087054,34838686,38742166,71067430 %N A015891 Numbers k such that k | 5^k + 5. %H A015891 Giovanni Resta, <a href="/A015891/b015891.txt">Table of n, a(n) for n = 1..100</a> %t A015891 Select[Range[1000000], IntegerQ[(PowerMod[5,#,# ]+5)/# ]&] (* _Alexander Adamchuk_ *) %Y A015891 Cf. A067946 = numbers n such that n divides 5^n-1. Cf. A015951 = numbers n such that n | 5^n + 1. %Y A015891 Cf. A006517, A015888, A015889, A015892, A015893, A015897, A015898, A015902, A015903, A015904, A015905, A015906. %K A015891 nonn %O A015891 1,2 %A A015891 _Robert G. Wilson v_ %E A015891 Corrected by _Alexander Adamchuk_, Nov 04 2006