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Search: id:A088987
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| A088987 |
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Triples of primes between two consecutive prime-index-primes. |
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+0
1
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| 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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: There cannot be an even number total of primes between two consecutive prime-index-primes.
The conjecture is true except for the first two prime-index primes (3 and 5), which have zero primes between them.
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EXAMPLE
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prime(prime(4)) = 17, prime(prime(5)) = 31. 19,23,29 are the "only" three primes between 17 and 31.
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PROGRAM
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(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", "); ); ) ) }
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CROSSREFS
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Sequence in context: A076056 A068654 A019384 this_sequence A019360 A007639 A108271
Adjacent sequences: A088984 A088985 A088986 this_sequence A088988 A088989 A088990
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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 31 2003
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EXTENSIONS
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Edited by T. D. Noe (noe(AT)sspectra.com), Apr 14 2009
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