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Search: id:A161850
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| A161850 |
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Subsequence of A161986 consisting of all terms that are prime. |
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+0
3
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| 7, 11, 13, 17, 19, 23, 29, 31, 37, 37, 41, 43, 47, 47, 53, 53, 59, 61, 67, 71, 71, 73, 79, 83, 89, 89, 97, 97, 101, 101, 103, 107, 109, 113, 127, 131, 137, 137, 139, 149, 149, 151, 157, 163, 163, 167, 167, 173, 179, 179, 181, 193, 191, 193, 197, 199, 211, 223, 227
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A161986(n) = k+r where where k is n-th composite and r is remainder of (largest prime divisor of k) divided by (smallest prime divisor k).
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EXAMPLE
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A161986(1) to A161986(27) are 4, 7, 8, 9, 11, 13, 15, 17, 16, 19, 21, 22, 23, 25, 25, 27, 27, 29, 31, 32, 35, 35, 37, 37, 39, 40, 41. Hence a(1) to a(11) are the prime terms among them, namely 7, 11, 13, 17, 19, 23, 29, 31 ,37, 37, 41.
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PROGRAM
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(MAGMA) [ p: n in [2..230] | not IsPrime(n) and IsPrime(p) where p is n+D[ #D] mod D[1] where D is PrimeDivisors(n) ];
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CROSSREFS
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Cf. A161986 (A002808(n)+A161849(n)), A002808 (composite numbers), A161849 (A052369(n) mod A056608(n)), A052369 (largest prime factor of n-th composite), A056608 (smallest divisor of n-th composite).
Sequence in context: A112588 A128974 A005776 this_sequence A007775 A070884 A135777
Adjacent sequences: A161847 A161848 A161849 this_sequence A161851 A161852 A161853
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jun 20 2009
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EXTENSIONS
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Edited and corrected (a(19)=57 replaced by 67; a(38)=137, a(49)=179, a(50)=179 inserted) by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Jun 24 2009
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