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A143265
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a(n) = the smallest integer >= n such that all the distinct primes that divide n and a(n) together are members of a set of consecutive primes. In other words, a(n) is the smallest integer >= n such that n*a(n) is contained in sequence A073491.
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0
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1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 11, 12, 13, 15, 15, 16, 17, 18, 19, 21, 25, 105, 23, 24, 25, 1155, 27, 30, 29, 30, 31, 32, 35, 15015, 35, 36, 37, 255255, 385, 42, 41, 45, 43, 105, 45, 4849845, 47, 48, 49, 51, 5005, 1155, 53, 54, 56, 60, 85085, 111546435, 59, 60, 61
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n) = A137795(n) * Ceiling(n/A137795(n)). [From Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 09 2008]
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EXAMPLE
| 20 is factored as 2^2 *5^1. Checking the integers >= 20: 20*20 is not factorable into consecutive primes, since 3 is missing. 21 is factored as 3^1 *7^1. Since the distinct primes that divide 20 and 21 (which are 2,3,5,7) form a set of consecutive primes, then a(20) = 21.
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CROSSREFS
| Cf. A073491, A137795.
Sequence in context: A029969 A029731 A029970 * A109841 A174234 A163807
Adjacent sequences: A143262 A143263 A143264 * A143266 A143267 A143268
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Aug 03 2008
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EXTENSIONS
| Inserted a(15) and a(21) and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 14 2008
a(46)-a(61) from Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 09 2008
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