

A087919


Indices for which there is at least one twin prime pair between two consecutive primeindexed primes.


0



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
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OFFSET

1,2


COMMENTS

It is not known whether there will always be instances where no twin prime pair exists between two consecutive primeindexed primes.


LINKS

Table of n, a(n) for n=1..69.


FORMULA

x such that prime(prime(x)) and prime(prime(x+1)) contain a twin prime pair.


EXAMPLE

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.


PROG

(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) ) ) }


CROSSREFS

Sequence in context: A194463 A140467 A103677 * A113508 A059325 A258938
Adjacent sequences: A087916 A087917 A087918 * A087920 A087921 A087922


KEYWORD

nonn


AUTHOR

Cino Hilliard, Oct 26 2003


STATUS

approved



