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Search: id:A070046
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| A070046 |
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Number of primes between prime(n) and 2prime(n) exclusive. |
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+0
4
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| 1, 1, 1, 2, 3, 3, 4, 4, 5, 6, 7, 9, 9, 9, 9, 11, 13, 12, 13, 14, 13, 15, 15, 16, 19, 20, 19, 19, 18, 18, 23, 23, 25, 25, 27, 26, 28, 28, 28, 28, 30, 30, 32, 32, 32, 32, 35, 38, 38, 38, 39, 39, 39, 41, 42, 43, 42, 42, 42, 42, 42, 44, 49, 50, 49, 49, 54, 54, 56, 55, 55, 55, 57, 58
(list; graph; listen)
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OFFSET
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1,4
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LINKS
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Eric Weisstein's World of Mathematics, Bertrand's Postulate
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EXAMPLE
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a(1)=1 because between p=2 and 4 there is exactly one prime, 3.
a(10)=6 since six consecutive primes (31,37,41,43,47,53) are located between p(10) = 29 and 58.
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PROGRAM
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(PARI) { forprime(p=2, 5000, n = -1; forprime(q=p+1, 50000, n++; if (q > p+p, print1(n, ", "); break ) ) )} - Harry J. Smith (hjsmithh(AT)sbcglobal.net), Dec 13 2007
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CROSSREFS
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Cf. A060715, A077463.
Sequence in context: A079420 A076895 A029086 this_sequence A130120 A164512 A127434
Adjacent sequences: A070043 A070044 A070045 this_sequence A070047 A070048 A070049
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KEYWORD
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easy,nonn
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), May 05 2002
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), May 15 2008 at the suggestion of R. J. Mathar
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