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A160598 Numerator of coresilience C(n) = (n - phi(n))/(n-1).

%I A160598 #14 Sep 08 2022 08:45:45
%S A160598 1,1,2,1,4,1,4,3,2,1,8,1,8,1,8,1,12,1,12,9,4,1,16,5,14,9,16,1,22,1,16,
%T A160598 13,6,11,24,1,20,15,8,1,30,1,24,21,8,1,32,7,30,19,28,1,36,5,32,3,10,1,
%U A160598 44,1,32,27,32,17,46,1,36,25,2,1,48,1,38,35,8,17,54,1,48,27,14,1,60,1
%N A160598 Numerator of coresilience C(n) = (n - phi(n))/(n-1).
%C A160598 Obviously C(p) = 1/(p-1), i.e., a(p)=1, for all primes p. Sequence A160599 lists composite numbers for which this is the case.
%H A160598 Vincenzo Librandi, <a href="/A160598/b160598.txt">Table of n, a(n) for n = 2..10000</a>
%H A160598 Project Euler, <a href="http://projecteuler.net/index.php?section=problems&amp;id=245">Problem 245: resilient fractions</a>, May 2009
%e A160598 a(10)=2 since for n=10, we have (n - phi(n))/(n-1) = (10-4)/9 = 2/3.
%t A160598 Numerator[Table[(n - EulerPhi[n])/(n - 1), {n, 2, 90}]] (* _Vincenzo Librandi_, Dec 27 2016 *)
%o A160598 (PARI) A160598(n)=numerator((n-eulerphi(n))/(n-1))
%o A160598 (Magma) [Numerator((n-EulerPhi(n))/(n-1)): n in [2..80]]; // _Vincenzo Librandi_, Dec 27 2016
%Y A160598 Cf. A160595, A160596, A160597, A160599.
%K A160598 nonn,frac
%O A160598 2,3
%A A160598 _M. F. Hasler_, May 23 2009