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A069926
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Number of k, 1<=k<=n, such that k divides sigma(k).
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0
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1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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FORMULA
| a(n)=Card(k: 1<=k<=n : sigma(k) == 0 (mod k) ) : asymptotically a(n)=C*ln(n)+o(ln(n)) with C=0, 7...
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PROG
| (PARI) for(n=1, 150, print1(sum(i=1, n, if(sigma(i)%(i), 0, 1)), ", "))
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CROSSREFS
| Sequence in context: A111892 A108248 A087104 * A077429 A204553 A060417
Adjacent sequences: A069923 A069924 A069925 * A069927 A069928 A069929
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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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