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 A233415 #12 Sep 09 2024 15:03:09 %S A233415 1,763425,10888425,40068105,142086921,191345625,462784725,468545025, %T A233415 552451809,595018305,683993905,956917125,1013987349,1024992045, %U A233415 1567781325,1581567885,3094868865,3312888345,4839991545,4882263477,5064476505,5613455925,7303900125 %N A233415 Odd numbers k such that 2k-1 divides 2^k-1. %C A233415 These seem to be much rarer than the corresponding even numbers. %H A233415 Charles R Greathouse IV, <a href="/A233415/b233415.txt">Table of n, a(n) for n = 1..51</a> %o A233415 (PARI) is(n)=n%2 && Mod(2, 2*n-1)^n==1 %Y A233415 Subsequence of A081856. %Y A233415 Numbers 2a(n)-1 form a subsequence of A187787. %K A233415 nonn %O A233415 1,2 %A A233415 _Charles R Greathouse IV_, Dec 09 2013