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Search: id:A073506
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| A073506 |
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Number of primes == 3 (mod 10) less than 10^n. |
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+0
4
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| 1, 7, 42, 310, 2402, 19665, 166230, 1440474, 12712499, 113765625
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also Pi(n,5,3)
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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Eric Weisstein's World of Mathematics, Modular Prime Counting Function
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EXAMPLE
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a(2)=7 because there are 7 primes == 3 (mod 10) less than 10^2. They are 3, 13, 23, 43, 53, 73 and 83.
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MATHEMATICA
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c = 0; k = 3; 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).
Adjacent sequences: A073503 A073504 A073505 this_sequence A073507 A073508 A073509
Sequence in context: A033133 A082035 A127016 this_sequence A025593 A048862 A133669
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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 (rgwv(AT)rgwv.com), Oct 03 2002
a(10) from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 22 2003
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