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A070243
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Card{ k, phi(k)<=n }.
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4
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2, 5, 5, 9, 9, 13, 13, 18, 18, 20, 20, 26, 26, 26, 26, 32, 32, 36, 36, 41, 41, 43, 43, 53, 53, 53, 53, 55, 55, 57, 57, 64, 64, 64, 64, 72, 72, 72, 72, 81, 81, 85, 85, 88, 88, 90, 90, 101, 101, 101, 101, 103, 103, 105, 105, 108, 108, 110, 110, 119, 119, 119, 119, 127, 127
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| G. Tenenbaum & Jie Wu, Exercices corriges de theorie analytique et probabiliste des nombres, Collection SMF, Cours specialises, Numero 2, pp. 78-79
S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 115-118.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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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 (benoit7848c(AT)orange.fr), Apr 12 2003
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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)), ", "))
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CROSSREFS
| Sequence in context: A200242 A062553 A126357 * A050175 A059797 A173567
Adjacent sequences: A070240 A070241 A070242 * A070244 A070245 A070246
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), May 11 2002
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