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Search: id:A157137
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| A157137 |
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Odd composite numbers n with equal number of prime digits in n and n-th prime. |
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+0
1
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| 15, 33, 39, 45, 75, 81, 85, 93, 115, 117, 123, 133, 141, 145, 169, 183, 185, 187, 195, 205, 207, 209, 213, 231, 243, 247, 259, 261, 273, 275, 287, 289, 295, 299, 301, 315, 321, 325, 333, 335, 339, 343, 363, 365, 385, 387, 391, 395, 427, 477, 505, 517, 527
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Prime digits are 2, 3, 5 or 7.
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EXAMPLE
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If prime(n=15=odd composite number)=47 and 1(5=prime)=1(7=prime), then 15=a(1). If prime(n=33=odd cohposite number)=137 and 2(3=prime and 3=prime)=2(3=prime and 7=prime), then 33=a(2). If prime(n=39=odd composite number)=167 and 1(3=prime)=1(7=prime), then 39=a(3), etc.
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CROSSREFS
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Cf. A000027, A000040, A155548.
Sequence in context: A068081 A089967 A064900 this_sequence A141230 A140608 A085371
Adjacent sequences: A157134 A157135 A157136 this_sequence A157138 A157139 A157140
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KEYWORD
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nonn,base
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)ramblerr), Feb 24 2009
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EXTENSIONS
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Corrected by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 26 2009
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