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 A065293 #20 Aug 02 2024 17:00:01
%S A065293 1,0,0,0,1,1,0,0,1,0,1,1,1,0,0,0,0,1,0,1,2,0,0,1,0,2,1,1,1,1,1,0,0,1,
%T A065293 1,1,0,1,2,1,1,1,0,0,3,0,0,1,1,2,0,1,2,1,0,2,0,2,0,1,1,1,1,0,2,1,0,0,
%U A065293 0,2,1,1,1,1,1,0,1,2,0,1,1,0,1,1,0,1,0,0,0,2,2,0,0,0,0,1,1,1,0,1,0,0,1,1,1
%N A065293 Number of values of s, 0 <= s <= n-1, such that 2^s mod n = s.
%H A065293 Michel Marcus, <a href="/A065293/b065293.txt">Table of n, a(n) for n = 1..1000</a>
%e A065293 For n=5 we have (2^0) mod 5 = 1, (2^1) mod 5 = 2, (2^2) mod 5 = 4, (2^3) mod 5 = 3, (2^4) mod 5 = 1. Only for s=3 does (2^s) mod 5=s, so a(5)=1
%t A065293 Table[Count[Range[0, n - 1], _?(Mod[2^#, n] == # &)], {n, 105}] (* _Michael De Vlieger_, Jun 19 2018 *)
%t A065293 Table[Count[Range[0,n-1],_?(PowerMod[2,#,n]==#&)],{n,110}] (* _Harvey P. Dale_, Aug 02 2024 *)
%o A065293 (PARI) a(n) = sum(s=0, n-1, Mod(2, n)^s == s); \\ _Michel Marcus_, Jun 19 2018
%Y A065293 Cf. A065294.
%K A065293 nonn
%O A065293 1,21
%A A065293 Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 28 2001
%E A065293 a(1) corrected by _Michel Marcus_, Jun 20 2018