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Search: id:A087919
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| A087919 |
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Indices for which there is at least one twin prime pair between two consecutive prime-index-primes. |
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+0
1
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| 1, 2, 3, 4, 6, 7, 8, 9, 11, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24, 25, 27, 29, 30, 34, 36, 39, 40, 42, 46, 47, 48, 50, 51, 54, 55, 56, 59, 61, 62, 63, 65, 66, 67, 68, 71, 74, 76, 77, 78, 79, 82, 86, 88, 90, 91, 92, 94, 95, 97, 99, 100, 101, 102, 103, 105, 106, 107, 110, 111
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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It is not known whether there will always be instances where no twin prime pair exists between two consecutive prime-index-primes.
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FORMULA
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x such that prime(prime(x)) and prime(prime(x+1)) contain a twin prime pair.
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EXAMPLE
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Prime(4)=17, prime(5)=31. Between 17 and 31 are two twin prime pairs: 17,19 and 29,31. prime(5) -> prime(6) = 31 -> 41 contain no twin prime pairs so 5 is not in the sequence.
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PROGRAM
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(PARI) piptwins(n) = { for(x=1, n, f=0; p1 = prime(prime(x)); p2 = prime(prime(x+1)); for(y=p1, p2, if(isprime(y) && y+2 <= p2 && isprime(y+2), print1(x", "); break) ) ) }
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CROSSREFS
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Adjacent sequences: A087916 A087917 A087918 this_sequence A087920 A087921 A087922
Sequence in context: A028237 A140467 A103677 this_sequence A113508 A059325 A004763
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Oct 26 2003
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