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A093683
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Number of pairs of twin primes <= 10^n-th prime.
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2
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OFFSET
| 1,1
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COMMENTS
| This sequence is >= the values of pi(10^n): 4, 25, 168, 1229, . . . in A006880
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REFERENCES
| Enoch Haga, "Wandering through a prime number desert," Table 6, in Exploring prime numbers on your PC and the Internet, 2001 (ISBN 1-885794-17-7)
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LINKS
| Thomas R. Nicely, Twin prime count
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FORMULA
| Count twin primes <= p_{10^n}: 10th prime, 100th prime, etc.
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EXAMPLE
| a(5)=10250 because that is the number of twin primes <= 1299709, the 100000-th prime
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MATHEMATICA
| NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; c = 0; p = q = 1; Do[l = Prime[10^n]; While[q <= l, If[p + 2 == q, c++ ]; p = q; q = NextPrim[p]]; Print[c], {n, 12}] (from Robert G. Wilson v Apr 10 2004)
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CROSSREFS
| See A049035 for another version. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 05 2008]
Cf. A006880 A007508 A049035.
Sequence in context: A140177 A034494 A084210 * A006348 A051820 A166697
Adjacent sequences: A093680 A093681 A093682 * A093684 A093685 A093686
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KEYWORD
| nonn
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Apr 09 2004
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