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Search: id:A107257
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| A107257 |
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Smallest prime p such that for each j <= n there are primes a < b <= p whose difference b - a is 2*j. |
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+0
1
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| 5, 7, 11, 11, 13, 17, 17, 19, 23, 23, 29, 29, 29, 31, 37, 37, 37, 41, 41, 43, 47, 47, 53, 53, 53, 59, 59, 59, 61, 67, 67, 67, 71, 71, 73, 79, 79, 79, 83, 83, 89, 89, 89, 101, 101, 101, 101, 101, 101, 103, 107, 107, 109, 113, 113, 131, 131, 131, 131, 131, 131, 131, 131
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Every positive even number <= 2*n is the difference of two suitable primes <= a(n).
Sequence is non-decreasing, whereas the related sequence A020484 is not; first divergence is at 45: a(45) = 101, A020484(45) = 97.
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EXAMPLE
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Consider n = 45. 89,97,101 are consecutive primes, 2*45 = 97 - 7, but 2*44
= 101 - 13 cannot be written as b - a where a and b are primes <=97, hence a(45) =
101.
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CROSSREFS
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Cf. A020484, A060264.
Sequence in context: A104200 A115044 A020484 this_sequence A098806 A122278 A124109
Adjacent sequences: A107254 A107255 A107256 this_sequence A107258 A107259 A107260
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KEYWORD
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nonn
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 15 2005
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