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 A177006 #24 Feb 11 2021 01:20:40
%S A177006 1,205505,3499105,4775905,6216001,27371265,270784801,477737601,
%T A177006 672819265,723513345,1237655809,1528531585,1732765105,2145938433,
%U A177006 2911107585,3214481761,3594908865,3912744705,3984159201,4356218881,4660483521,5089667905,5572247601,5628702769
%N A177006 Nonprime numbers k such that k^k == 1 (mod phi(k)).
%C A177006 For all primes p we have p^p == 1 (mod phi(p)), because p = phi(p) + 1.
%C A177006 All terms are squarefree.
%C A177006 If k is a composite number such that phi(k) divides k-1 then k is in the sequence. What is the first such number? - _Jahangeer Kholdi_, Dec 10 2014
%C A177006 All terms are odd. - _Robert Israel_, Dec 12 2014
%H A177006 Giovanni Resta, <a href="/A177006/b177006.txt">Table of n, a(n) for n = 1..51</a>
%e A177006 205505 is a nonprime number, phi(205505) = 157168 and 205505^205505 == 1 (mod 157168) so 205505 is in the sequence.
%t A177006 v={1}; Do[If[ !PrimeQ[n]&&PowerMod[n,n,EulerPhi[n]]==1,AppendTo[v,n];
%t A177006 Print[v]],{n,200000000}]
%o A177006 (PARI) is(n)=Mod(n,eulerphi(n))^n==1 && !isprime(n) \\ _Charles R Greathouse IV_, Dec 11 2014
%Y A177006 Cf. A000010, A177012.
%K A177006 nonn
%O A177006 1,2
%A A177006 _Farideh Firoozbakht_, May 19 2010
%E A177006 a(7)-a(8) from _Jahangeer Kholdi_, Dec 10 2014
%E A177006 a(9)-a(13) from _Jahangeer Kholdi_, Dec 11 2014
%E A177006 a(14)-a(24) from _Giovanni Resta_, Apr 28 2017