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1, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 9, 10, 11, 11, 11, 12, 12, 13, 14, 14, 15, 15, 15, 16, 16, 16, 17, 18, 18, 18, 19, 19, 20, 21, 21, 21, 22, 22, 23, 23, 23, 24, 24, 24, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 30, 30, 30, 30, 30, 30, 31, 31, 32, 32, 32, 33, 34, 34, 34, 34, 34
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Maximal number of primes possible in a string of 2n consecutive numbers. - Lekraj Beedassy (blekraj(AT)yahoo.com), Dec 04 2004
a(n) = A139325(n,1) + 1. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 14 2008
Or the number of primes<=2*n. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Oct 29 2009]
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FORMULA
| a(n) = A000720(n) + A035250(n) - A010051(n). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 05 2010]
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MAPLE
| with(numtheory):seq(pi(2*n), n=1..86); (Deutsch)
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PROG
| (Other) sage: [prime_pi(2*n) for n in xrange(1, 75)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 06 2009]
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CROSSREFS
| Sequence in context: A080444 A082288 A099801 * A196266 A112232 A168389
Adjacent sequences: A099799 A099800 A099801 * A099803 A099804 A099805
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Nov 19 2004
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 12 2005
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