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 A015958 #21 Mar 20 2020 20:08:50 %S A015958 1,11,121,253,1331,2783,5819,11891,14641,30613,35167,45023,64009, %T A015958 96569,130801,133837,161051,273493,336743,386837,495253,527197,558877, %U A015958 640343,704099,808841,1035529,1062259,1438811,1472207,1652849,1771561,2221087,3008423,3045449 %N A015958 Numbers k such that k | 10^k + 1. %H A015958 Seiichi Manyama, <a href="/A015958/b015958.txt">Table of n, a(n) for n = 1..100</a> %t A015958 Select[Range[15*10^5],PowerMod[10,#,#]==#-1&] (* _Harvey P. Dale_, Oct 01 2017 *) %Y A015958 Solutions to b^k == -1 (mod k): A006521 (b=2), A015949 (b=3), A015950 (b=4), A015951 (b=5), A015953 (b=6), A015954 (b=7), A015955 (b=8), A015957 (b=9), this sequence (b=10), A015960 (b=11), A015961 (b=12), A015963 (b=13), A015965 (b=14), A015968 (b=15), A015969 (b=16). %Y A015958 Column k=10 of A333429. %K A015958 nonn %O A015958 1,2 %A A015958 _Robert G. Wilson v_ %E A015958 Corrected by _T. D. Noe_, Oct 31 2006