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A073505
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Number of primes == 1 (mod 10) less than 10^n.
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4
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OFFSET
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1,2
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COMMENTS
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Also Pi(n,5,1)
This and the related sequences A073505-A073517 and A002280, A073548-A073565 are included because there is interest in the distribution of primes by their initial or final digits.
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LINKS
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Table of n, a(n) for n=1..10.
Eric Weisstein's World of Mathematics, Modular Prime Counting Function
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EXAMPLE
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a(2)=5 because there are 5 primes == 1 (mod 10) less than 10^2. They are 11, 31, 41, 61 and 71.
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MATHEMATICA
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c = 0; k = 1; Do[While[k < 10^n, If[PrimeQ[k], c++ ]; k += 10]; Print[c], {n, 1, 10}]
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CROSSREFS
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Cf. A073509 to A073517. A073505(n) + A073506(n) + A073507(n) + A073508(n) + 1 = A006880(n).
Sequence in context: A124545 A125729 A144069 * A145841 A123943 A067412
Adjacent sequences: A073502 A073503 A073504 * A073506 A073507 A073508
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KEYWORD
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base,nonn
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AUTHOR
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Shyam Sunder Gupta (guptass(AT)rediffmail.com), Aug 14 2002
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EXTENSIONS
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Edited by Robert G. Wilson v, Oct 03 2002
a(10) from Robert G. Wilson v, Dec 22 2003
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STATUS
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approved
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