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A104904
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Numbers n such that d(n)*pi(n)=n, where d(n) is the number of positive divisors of n.
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2
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OFFSET
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1,1
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COMMENTS
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Next term is greater than 3*10^9.
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LINKS
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Table of n, a(n) for n=1..8.
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EXAMPLE
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189961452 is in the sequence because d(189961452)=18; pi(189961452)=10553414 & 18*10553414=189961452.
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MATHEMATICA
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Do[If[DivisorSigma[0, n]*PrimePi[n] == n, Print[n]], {n, 2000000000}]
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CROSSREFS
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Cf. A063903, A104905, A104906.
Sequence in context: A322126 A272241 A171939 * A272247 A167748 A203755
Adjacent sequences: A104901 A104902 A104903 * A104905 A104906 A104907
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KEYWORD
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hard,more,nonn
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AUTHOR
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Farideh Firoozbakht, Apr 12 2005
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EXTENSIONS
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a(5)-a(8) from Donovan Johnson, Dec 08 2009
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STATUS
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approved
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