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A069924
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Number of k, 1<=k<=n, such that phi(k) divides k.
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0
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1, 2, 2, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n)=Card(k: 1<=k<=n : k==0 (mod phi(k))) asymptotically : a(n)=C*ln(n)^2+o(ln(n)^2) with C=0, 6....
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PROG
| (PARI) for(n=1, 150, print1(sum(i=1, n, if(i%eulerphi(i), 0, 1)), ", "))
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CROSSREFS
| Sequence in context: A140828 A035100 A085089 * A082479 A090616 A186704
Adjacent sequences: A069921 A069922 A069923 * A069925 A069926 A069927
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), May 05 2002
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