OFFSET
1,2
COMMENTS
Limit_{n->oo} a(n) * log(log(log(n))) / n = 1/exp(gamma).
REFERENCES
Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 115-119.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
P. Erdős, Some asymptotic formulas in number theory, J. Indian Math. Soc. 12 (1948) 75-78.
Steven R. Finch, Euler Totient Function Asymptotic Constants [Broken link]
Steven R. Finch, Euler Totient Function Asymptotic Constants [From the Wayback machine]
Paul Pollack, Numbers which are orders only of cyclic groups, arXiv:2007.09734 [math.NT], 2020.
Z. Ruzsa, Erdős and the integers, J. Number Theory 79 (1999) 115-163.
FORMULA
PROG
(PARI) a(n) = sum(k=1, n, gcd(k, eulerphi(k)) == 1) \\ Charles R Greathouse IV, Jan 29 2013 (corrected by Iain Fox, Dec 25 2017)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Frank Ellermann, May 29 2001
STATUS
approved