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Search: id:A089452
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| A089452 |
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a(n) = smallest prime k such that k*(p(n)-1) + p(n) is prime, where p(n) = n-th prime. |
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1
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| 2, 2, 2, 2, 2, 5, 3, 2, 3, 5, 2, 5, 2, 2, 2, 3, 2, 2, 2, 5, 3, 113, 3, 5, 3, 2, 29, 3, 2, 2, 3, 2, 5, 3, 3, 5, 2, 2, 5, 5, 2, 2, 2, 17, 11, 2, 7, 11, 19, 3, 3, 13, 2, 2, 2, 5, 2, 2, 11, 3, 2, 2, 5, 2, 11, 2, 2, 2, 5, 3, 3, 19, 2, 5, 5, 3, 5, 2, 19, 5, 2, 2, 3, 2, 5, 17, 2, 7, 2, 3, 2, 2, 3, 5, 3, 2, 2, 11, 2
(list; graph; listen)
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OFFSET
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3,1
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COMMENT
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Does every prime appear in this sequence? - Gabriel Cunningham (gcasey(AT)mit.edu), Mar 27 2004
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EXAMPLE
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a(2)=2 because 2*(p(2)-1) + p(2) = 7, which is prime. a(7)=5 because 2*(p(7)-1) + p(7) = 49 and 3*(p(7)-1) + p(7) = 65, both of which are composite, but 5*(p(7)-1) + p(7) = 97, which is prime.
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PROGRAM
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(PARI) diff2sqp2(n) = { forprime(q=3, n, forprime(p=3, n, y=(p-q)/(q-1); if(y==floor(y), if(isprime(y), print1(y", "); break) ) ) ) }
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CROSSREFS
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Adjacent sequences: A089449 A089450 A089451 this_sequence A089453 A089454 A089455
Sequence in context: A083499 A029103 A008737 this_sequence A115101 A023569 A051887
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Dec 28 2003
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EXTENSIONS
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More terms from Gabriel Cunningham (gcasey(AT)mit.edu), Mar 27 2004
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