OFFSET
2,3
COMMENTS
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.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 2..10000
Project Euler, Problem 245: resilient fractions, May 2009
EXAMPLE
a(10)=2 since for n=10, we have (n - phi(n))/(n-1) = (10-4)/9 = 2/3.
MATHEMATICA
Numerator[Table[(n - EulerPhi[n])/(n - 1), {n, 2, 90}]] (* Vincenzo Librandi, Dec 27 2016 *)
PROG
(PARI) A160598(n)=numerator((n-eulerphi(n))/(n-1))
(Magma) [Numerator((n-EulerPhi(n))/(n-1)): n in [2..80]]; // Vincenzo Librandi, Dec 27 2016
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
M. F. Hasler, May 23 2009
STATUS
approved