

A160597


Denominator of coresilience C(n) = (n  phi(n))/(n1).


3



1, 2, 3, 4, 5, 6, 7, 8, 3, 10, 11, 12, 13, 2, 15, 16, 17, 18, 19, 20, 7, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 11, 34, 35, 36, 37, 38, 13, 40, 41, 42, 43, 44, 15, 46, 47, 48, 49, 50, 51, 52, 53, 18, 55, 8, 19, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 3, 70, 71, 72, 73, 74
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OFFSET

2,2


COMMENTS

Obviously C(p) = 1/(p1) for all primes p.


LINKS

Robert Israel, Table of n, a(n) for n = 2..10000
Project Euler, Problem 245: resilient fractions, May 2009


EXAMPLE

a(10)=3 since for n=10, we have (n  phi(n))/(n1) = (104)/9 = 2/3.


MAPLE

seq(denom((nnumtheory:phi(n))/(n1)), n=2..100); # Robert Israel, Dec 26 2016


MATHEMATICA

Denominator[Table[(n  EulerPhi[n])/(n  1), {n, 2, 20}]] (* G. C. Greubel, Dec 26 2016 *)


PROG

(PARI) A160597(n)=denominator((neulerphi(n))/(n1))
(MAGMA) [Denominator((nEulerPhi(n))/(n1)): n in [2..80]]; // Vincenzo Librandi, Dec 27 2016


CROSSREFS

Cf. A160598.
Sequence in context: A238593 A279649 A278060 * A282779 A305902 A245350
Adjacent sequences: A160594 A160595 A160596 * A160598 A160599 A160600


KEYWORD

nonn,frac,look


AUTHOR

M. F. Hasler, May 23 2009


STATUS

approved



