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 A015953 #20 Mar 20 2020 19:38:00 %S A015953 1,7,49,203,343,1379,1421,2401,5887,9653,9947,11977,16807,39991,41209, %T A015953 67571,69629,83839,117649,170723,271663,279937,288463,347333,472997, %U A015953 487403,586873,706643,823543,1159739,1195061,1901641,1959559,2019241,2359469,2431331 %N A015953 Numbers k such that k | 6^k + 1. %H A015953 Seiichi Manyama, <a href="/A015953/b015953.txt">Table of n, a(n) for n = 1..100</a> %t A015953 Select[Range[2000000],PowerMod[6,#,#]==#-1&] (* _Harvey P. Dale_, Aug 28 2012 *) %Y A015953 Solutions to b^k == -1 (mod k): A006521 (b=2), A015949 (b=3), A015950 (b=4), A015951 (b=5), this sequence (b=6), A015954 (b=7), A015955 (b=8), A015957 (b=9), A015958 (b=10), A015960 (b=11), A015961 (b=12), A015963 (b=13), A015965 (b=14), A015968 (b=15), A015969 (b=16). %Y A015953 Column k=6 of A333429. %K A015953 nonn %O A015953 1,2 %A A015953 _Robert G. Wilson v_