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 A091847 #14 Mar 24 2023 12:42:35
%S A091847 15,39,111,183,255,327,363,471,2199,3063,4359,4375,5571,8751,15723,
%T A091847 36759,46791,65535,140103,208191,441027,4190263,9056583,57395631,
%U A091847 172186887,236923383,918330183,3932935775,4294967295,4764161215
%N A091847 Perfect totient numbers, omitting powers of 3.
%H A091847 Douglas E. Iannucci, Deng Moujie and Graeme L. Cohen, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL6/Cohen2/cohen50.html">On Perfect Totient Numbers</a>, J. Integer Seqs., Vol. 6, 2003.
%t A091847 fQ[n_] := !IntegerQ@ Log[3, n] && Plus @@ FixedPointList[ EulerPhi@# &, n] == 2n + 1 (* _Robert G. Wilson v_, Nov 06 2010 *)
%o A091847 (Python)
%o A091847 from itertools import count, islice
%o A091847 from gmpy2 import digits
%o A091847 from sympy import totient
%o A091847 def A091847_gen(startvalue=3): # generator of terms >= startvalue
%o A091847 for n in count((k:=max(startvalue,3))+1-(k&1),2):
%o A091847 t = digits(n,3)
%o A091847 if t.count('0') != len(t)-1:
%o A091847 m, s = n, 1
%o A091847 while (m:=totient(m))>1:
%o A091847 s += m
%o A091847 if s == n:
%o A091847 yield n
%o A091847 A091847_list = list(islice(A091847_gen(),10)) # _Chai Wah Wu_, Mar 24 2023
%Y A091847 A082897 has more information.
%K A091847 nonn
%O A091847 1,1
%A A091847 _N. J. A. Sloane_, Mar 13 2004