%I #26 Apr 15 2017 09:32:26
%S 1,1,3,3,15,3,63,15,63,15,1023,15,4095,63,255,255,65535,63,262143,255,
%T 4095,1023,4194303,255,1048575,4095,262143,4095,268435455,255,
%U 1073741823,65535,1048575,65535,16777215,4095,68719476735,262143,16777215,65535
%N a(n) = 2^phi(n) - 1 = A066781(n) - 1.
%C Number of nonempty subsets of reduced residue system [RRS(n)] modulo n.
%H T. D. Noe, <a href="/A100371/b100371.txt">Table of n, a(n) for n = 1..1000</a>
%H 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 a(n) = Sum_{i=1..n} binomial(phi(n), i). - _Enrique PĂ©rez Herrero_, Mar 10 2012
%p A100371:=n->2^numtheory[phi](n)-1: seq(A100371(n), n=1..60); # _Wesley Ivan Hurt_, Apr 14 2017
%t Table[2^EulerPhi[n] - 1, {n, 1, 50}]
%o (PARI) a(n) = 2^eulerphi(n) - 1; \\ _Michel Marcus_, Apr 14 2017
%o (Python)
%o from sympy import totient
%o def a(n): return 2**totient(n) - 1 # _Indranil Ghosh_, Apr 14 2017
%Y Cf. A000010, A066781.
%K easy,nonn
%O 1,3
%A _Labos Elemer_, Nov 30 2004
%E Entry revised by _N. J. A. Sloane_, Jun 07 2013
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