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A158337
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Composite numbers k such that k - number of prime factors of k = prime.
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0
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4, 8, 9, 15, 20, 21, 25, 33, 39, 44, 48, 49, 50, 55, 69, 70, 72, 76, 85, 91, 92, 108, 110, 111, 112, 115, 116, 129, 130, 133, 135, 141, 154, 159, 162, 168, 169, 170, 182, 183, 201, 213, 230, 235, 236, 242, 244, 253, 259, 265, 266, 284, 286, 288, 295, 297, 309
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| If composite=4=2*2 and 4-2=2=prime, then 4=a(1). If composite=8=2*2*2 and 8-3=5=prime, then 8=a(2). If compsite =9=3*3=and 9-2=7=prime, then 9=a(3), etc.
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CROSSREFS
| Cf. A000040, A002808.
Sequence in context: A137055 A078177 A023886 * A161542 A131195 A020217
Adjacent sequences: A158334 A158335 A158336 * A158338 A158339 A158340
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KEYWORD
| nonn
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AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Mar 16 2009, Nov 14 2009
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EXTENSIONS
| Entries checked by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 19 2010
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