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Search: id:A074810
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| A074810 |
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Number of primes between n and 2n (inclusive) = largest prime factor of n. |
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+0
1
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| 1, 2, 4, 8, 9, 28, 65, 114, 174, 186, 246, 623, 1784, 1832, 1912, 5121, 13810, 14090, 39413, 40403, 808822, 809858, 810026
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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a(6) = 28 because there are 7 primes between n = 28 and 2n = 56: 29, 31, 37, 41, 43, 47, 53; and the largest prime dividing 28 is 7.
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MAPLE
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with(numtheory): a:=proc(n) if pi(2*n)-pi(n-1)=factorset(n)[nops(factorset(n))] then n else fi end: 1, seq(a(n), n=2..1000); (Deutsch)
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CROSSREFS
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Cf. A035250, A006530.
Sequence in context: A140141 A088274 A118418 this_sequence A028984 A043706 A028836
Adjacent sequences: A074807 A074808 A074809 this_sequence A074811 A074812 A074813
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Sep 08 2002
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 05 2006
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