A088987 Triples of primes between two consecutive prime-indexed primes.

19, 23, 29, 43, 47, 53, 71, 73, 79, 163, 167, 173, 193, 197, 199, 337, 347, 349, 409, 419, 421, 521, 523, 541, 569, 571, 577, 601, 607, 613, 719, 727, 733, 971, 977, 983, 1181, 1187, 1193, 1423, 1427, 1429, 1451, 1453, 1459, 1789, 1801, 1811, 2029, 2039, 2053

Offset

1,1

Comments

Conjecture: There cannot be an even number total of primes between two consecutive prime-indexed primes.

The conjecture is true except for the first two prime-indexed primes (3 and 5), which have zero primes between them.

Links

Table of n, a(n) for n=1..51.

Example

prime(prime(4)) = 17, prime(prime(5)) = 31. 19,23,29 are the "only" three primes between 17 and 31.

Prog

(PARI) pipprimes(n, m) = { for(x=1, n, c=0; p1 = prime(prime(x)); p2 = prime(prime(x+1)); forprime(y=p1+2, p2-2, c++); if(c==m, forprime(y=p1+2, p2-2, print1(y", "); ); ) ) }

Crossrefs

Sequence in context: A286415 A305835 A019384 * A364458 A217281 A322960

Adjacent sequences: A088984 A088985 A088986 * A088988 A088989 A088990

Keyword

nonn

Author

Cino Hilliard, Oct 31 2003

Extensions

Edited by T. D. Noe, Apr 14 2009

Status

approved