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Search: id:A104200
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| A104200 |
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Upper bound on a straddle prime pair. |
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+0
1
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| 5, 7, 11, 11, 11, 13, 17, 17, 17, 19, 23, 23, 23, 29, 29, 29, 29, 29, 31, 37, 37, 37, 37, 37, 41, 41, 41, 43, 47, 47, 47, 53, 53, 53, 53, 53, 59, 59, 59, 59, 59, 61, 67, 67, 67, 67, 67, 71, 71, 71, 73, 79, 79, 79, 79, 79, 83, 83, 83, 89, 89, 89, 89, 89, 97, 97, 97, 97, 97, 97
(list; graph; listen)
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OFFSET
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4,1
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COMMENT
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Straddle primes that occur only once on either side of the composite number are lower and upper twin primes respectively.
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FORMULA
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Straddle primes are the nearest primes preceding and following composite n.
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EXAMPLE
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The first straddle prime pair is 3 and 5 which straddles the composite number
4.
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PROGRAM
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(PARI) \Straddle primes - largest prime preceding composite n and smallest \prime following n. strad(n) = { local (x, y, pp, np); for(x=1, n, y=composite(x); pp=precprime(y); np=nextprime(y); print1(np", ") ) }
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CROSSREFS
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Sequence in context: A023590 A096919 A023594 this_sequence A115044 A020484 A107257
Adjacent sequences: A104197 A104198 A104199 this_sequence A104201 A104202 A104203
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Mar 13 2005
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