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A099078
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Numbers n such that pi(n).pi(n-1) ... pi(3).pi(2) is prime (dot between numbers means concatenation).
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3
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OFFSET
| 1,1
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COMMENTS
| Number of digits of primes corresponding to the five known terms of this sequence are respectively 4,21,67,605,1633.
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LINKS
| C. Rivera, ,Primes by Listing, The Prime Puzzles & Problems connection.
Eric Weisstein ,A Section of The World of Mathematics
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EXAMPLE
| 5 is in the sequence because pi(5).pi(4).pi(3).pi(2)=3221 is prime.
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MATHEMATICA
| s = ""; Do[s = ToString[PrimePi[n]] <> s; k = ToExpression[s]; If[PrimeQ[k], Print[n]], {n, 2, 5235}] (Propper)
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CROSSREFS
| Cf. A046035, A099077, A099079, A099080.
Sequence in context: A085101 A184724 A082005 * A049452 A033445 A050533
Adjacent sequences: A099075 A099076 A099077 * A099079 A099080 A099081
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KEYWORD
| base,more,nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Oct 23 2004
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EXTENSIONS
| One more term from Ryan Propper (rpropper(AT)stanford.edu), Aug 30 2005
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