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Search: id:A073703
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| A073703 |
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Smallest prime p such that also p+prime(n)*2 is a prime. |
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15
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| 3, 5, 3, 3, 7, 3, 3, 3, 7, 3, 5, 5, 7, 3, 3, 3, 13, 5, 3, 7, 3, 5, 7, 3, 3, 31, 5, 13, 5, 3, 3, 7, 3, 3, 13, 5, 3, 5, 3, 3, 31, 5, 7, 3, 3, 3, 11, 3, 3, 3, 13, 13, 5, 7, 7, 31, 3, 5, 3, 7, 3, 7, 3, 19, 5, 7, 11, 3, 7, 3, 3, 43, 5, 5, 3, 3, 19, 3, 7, 3, 19, 11, 19, 11, 3, 43, 13, 5, 7, 3, 3, 13, 3
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If Polignac's conjecture (1849) is correct, the sequence is defined for all n (as is A020483).
Also: least k-prime(n) such that k-prime(n) and k+prime(n) are both primes. - Pierre CAMI (pierrecami(AT)tele2.fr), Aug 27 2004
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EXAMPLE
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n=5: prime(5)=11; 2+11*2=24, 3+11*2=25 and 5+11*2=27 are not prime, but 7+11*2=29 is prime, therefore a(5)=7.
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MATHEMATICA
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f[n_] := Block[{k = Prime[n], p = Prime[n]}, While[ !PrimeQ[k - p] || !PrimeQ[k + p], k++ ]; k - p]; Table[ f[n], {n, 95}] (from Robert G. Wilson v Aug 28 2004)
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CROSSREFS
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Cf. A073704, A001747, A000040, A020483.
Sequence in context: A021287 A124887 A097524 this_sequence A097519 A133773 A077934
Adjacent sequences: A073700 A073701 A073702 this_sequence A073704 A073705 A073706
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 04 2002
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EXTENSIONS
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Merged with Pierre CAMI's submission of Aug 2004 - R. J. Mathar Jul 29 2008
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