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 A100371 #26 Apr 15 2017 09:32:26
%S A100371 1,1,3,3,15,3,63,15,63,15,1023,15,4095,63,255,255,65535,63,262143,255,
%T A100371 4095,1023,4194303,255,1048575,4095,262143,4095,268435455,255,
%U A100371 1073741823,65535,1048575,65535,16777215,4095,68719476735,262143,16777215,65535
%N A100371 a(n) = 2^phi(n) - 1 = A066781(n) - 1.
%C A100371 Number of nonempty subsets of reduced residue system [RRS(n)] modulo n.
%H A100371 T. D. Noe, <a href="/A100371/b100371.txt">Table of n, a(n) for n = 1..1000</a>
%H A100371 N. Bliss, B. Fulan, S. Lovett, and J. Sommars, <a href="http://dx.doi.org/10.4169/amer.math.monthly.120.06.519">Strong Divisibility, Cyclotomic Polynomials, and Iterated Polynomials</a>, Amer. Math. Monthly, 120 (2013), 519-536.
%F A100371 a(n) = Sum_{i=1..n} binomial(phi(n), i). - _Enrique Pérez Herrero_, Mar 10 2012
%p A100371 A100371:=n->2^numtheory[phi](n)-1: seq(A100371(n), n=1..60); # _Wesley Ivan Hurt_, Apr 14 2017
%t A100371 Table[2^EulerPhi[n] - 1, {n, 1, 50}]
%o A100371 (PARI) a(n) = 2^eulerphi(n) - 1; \\ _Michel Marcus_, Apr 14 2017
%o A100371 (Python)
%o A100371 from sympy import totient
%o A100371 def a(n): return 2**totient(n) - 1 # _Indranil Ghosh_, Apr 14 2017
%Y A100371 Cf. A000010, A066781.
%K A100371 easy,nonn
%O A100371 1,3
%A A100371 _Labos Elemer_, Nov 30 2004
%E A100371 Entry revised by _N. J. A. Sloane_, Jun 07 2013