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%I #6 Jan 07 2017 02:46:33
%S 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,
%T 39,40,42,46,47,48,50,51,54,55,56,59,61,62,63,65,66,67,68,71,74,76,77,
%U 78,79,82,86,88,90,91,92,94,95,97,99,100,101,102,103,105,106,107,110,111
%N Indices for which there is at least one twin prime pair between two consecutive prime-indexed primes.
%C It is not known whether there will always be instances where no twin prime pair exists between two consecutive prime-indexed primes.
%F x such that prime(prime(x)) and prime(prime(x+1)) contain a twin prime pair.
%e 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.
%o (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) ) ) }
%K nonn
%O 1,2
%A _Cino Hilliard_, Oct 26 2003
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