OFFSET
1,1
REFERENCES
G. Tenenbaum & Jie Wu, Exercices corrigés de théorie analytique et probabiliste des nombres, Collection SMF, Cours specialises, Numero 2, pp. 78-79.
S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 115-118.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
Matteo Caorsi, Sergio Cecotti, Geometric classification of 4d N=2 SCFTs, arXiv:1801.04542 [hep-th], 2018.
FORMULA
Lim_{n ->infinity} a(n)/n = zeta(2)zeta(3)/zeta(6) = 1.943596436820759205057... = A082695.
a(n) = Sum_{k=1..n} A014197(k); a(n) = zeta(2)*zeta(3)/zeta(6)*n + O(n*exp(-c*sqrt(log(n))) for a suitable constant c > 0. - Benoit Cloitre, Apr 12 2003
PROG
(PARI) for(n=1, 150, print1(sum(i=1, 100*n, if(sign(eulerphi(i)-n)+1, 0, 1)+if((eulerphi(i)-n), 0, 1)), ", "))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 11 2002
STATUS
approved