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Search: id:A087920
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| A087920 |
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Indices for which there is no twin prime pair between two consecutive prime-index-primes. |
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+0
1
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| 5, 10, 12, 20, 21, 26, 28, 31, 32, 33, 35, 37, 38, 41, 43, 44, 45, 49, 52, 53, 57, 58, 60, 64, 69, 70, 72, 73, 75, 80, 81, 83, 84, 85, 87, 89, 93, 96, 98, 104, 108, 109, 113, 116, 118, 120, 124, 126, 130, 134, 140, 142, 143, 147, 152, 155, 159, 163, 164, 165, 169, 171
(list; graph; listen)
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OFFSET
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1,1
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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 no twim prime pair.
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EXAMPLE
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Prime(5) -> prime(6) = 31 -> 41 contains no twin prime pairs, so 5 is in the sequence.
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PROGRAM
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(PARI) piptwins2(n) = { for(x=1, n, f=1; p1 = prime(prime(x)); p2 = prime(prime(x+1)); for(y=p1, p2, if(isprime(y) && y+2 <= p2 && isprime(y+2), f=0) ); if(f, print1(x", ")) ) }
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CROSSREFS
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Adjacent sequences: A087917 A087918 A087919 this_sequence A087921 A087922 A087923
Sequence in context: A112776 A120063 A101839 this_sequence A103676 A129846 A001974
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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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