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Search: id:A104199
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| A104199 |
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Lower bound on a straddle prime pair. |
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+0
1
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| 3, 5, 7, 7, 7, 11, 13, 13, 13, 17, 19, 19, 19, 23, 23, 23, 23, 23, 29, 31, 31, 31, 31, 31, 37, 37, 37, 41, 43, 43, 43, 47, 47, 47, 47, 47, 53, 53, 53, 53, 53, 59, 61, 61, 61, 61, 61, 67, 67, 67, 71, 73, 73, 73, 73, 73, 79, 79, 79, 83, 83, 83, 83, 83, 89, 89, 89, 89, 89, 89, 89
(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 a composite number n.
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EXAMPLE
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The first straddle prime pair is 3 and 5 which straddle 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(pp", ") ) }
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CROSSREFS
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Adjacent sequences: A104196 A104197 A104198 this_sequence A104200 A104201 A104202
Sequence in context: A130159 A127314 A092257 this_sequence A103470 A064002 A109535
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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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