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Search: id:A158340
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| A158340 |
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Composite numbers k such that number of prime factors of k + number of divisors of k = prime. |
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+0
1
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| 4, 8, 9, 25, 27, 30, 32, 36, 42, 49, 64, 66, 70, 72, 78, 100, 102, 105, 108, 110, 114, 121, 125, 130, 148, 154, 165, 170, 174, 180, 182, 186, 190, 195, 196, 200, 222, 225, 230, 231, 238, 243, 246, 252, 255, 256, 258, 266, 273, 282, 285, 286, 290, 300, 310, 318, 322
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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If composite=2*2=4(1, 2, 4) and 2+3=5=prime, then 4=a(1). If composite=2*2*2=8(1, 2, 4, 8) and 3+4=7=prime, then 8=a(2). If composite=9=3*3=9(1, 3, 9) and 2+3=5=prime, then 9=a(3), etc.
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CROSSREFS
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Cf. A000040, A002808, A035004.
Adjacent sequences: A158337 A158338 A158339 this_sequence A158341 A158342 A158343
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KEYWORD
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nonn,new
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Mar 16 2009, Nov 14 2009
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