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A163769
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Primes p such that 2*p+3 is not prime.
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0
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3, 11, 23, 31, 37, 41, 59, 61, 71, 79, 83, 101, 103, 107, 109, 131, 149, 151, 163, 179, 181, 191, 211, 233, 239, 241, 251, 257, 263, 271, 281, 293, 311, 313, 317, 331, 347, 359, 367, 373, 389, 401, 419, 421, 431, 433, 443, 449, 457, 461, 479, 491, 499, 521
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| All those p appear in A144562. [Proof: since 2p+3 is odd and not prime, it can be written as a product of two odd numbers, 2p+3=(2k+1)*(2s+1), therefore p=2ks+k+s-1 - R. J. Mathar Aug 06 2009]
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FORMULA
| A153238 INTERSECT A000040. - R. J. Mathar, (mathar(AT)strw.leidenuniv.nl), Aug 05 2009
A000040 \ A023204. - R. J. Mathar, (mathar(AT)strw.leidenuniv.nl), Aug 05 2009
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EXAMPLE
| For p=3, 2*p+3=9. For p=11, 2*p+3=25. For p=23, 2*p+3=49.
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MATHEMATICA
| Select[Prime[Range[200]], !PrimeQ[2#+3]&] (* From Harvey P. Dale, Feb 02 2012 *)
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CROSSREFS
| Cf. A144562
Sequence in context: A141226 A049491 A000355 * A100860 A018630 A163780
Adjacent sequences: A163766 A163767 A163768 * A163770 A163771 A163772
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KEYWORD
| nonn,easy,changed
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2009
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EXTENSIONS
| Entries checked - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 06 2009
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