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A158509
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Prime(n-1) such that prime(n-1)+5 is square and equal to prime(n+1)-1.
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0
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11, 191, 495611, 1628171, 1893371, 7806431, 14167691, 15085451, 16048031, 20124191, 23951231, 27415691, 28558331, 30096191, 41396351, 46022651, 55591931, 87871871, 88811771, 99720191, 103347551, 130051211
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OFFSET
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2,1
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COMMENTS
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Conjecture: If the condition holds, prime(n-1) and prime(n) are twin primes of the form 10k+1 and 10k+3. Ie., the last digits of the primes are 1 and 3. The 1 ending is evident in the entries here.
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LINKS
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Table of n, a(n) for n=2..23.
S. M. Ruiz, Integer then equal.
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FORMULA
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Prime(n) is the n-th prime number.
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EXAMPLE
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For n = 6, prime(6-1)=11,11+5=16;prime(6+1)=17,17-1=16. So prime(6-1)=11 is the first entry in the sequence.
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PROG
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(PARI) integerequal(m, n, a, b) =
{
local(x, p1, p2);
for(x=m, n,
p1=prime(x-1);
if(issquare(p1+a),
p2=prime(x+1); if((p1+a)==(p2-b),
print(x", "p1", "prime(x))
)
)
)
}
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CROSSREFS
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Sequence in context: A002195 A171553 A068649 * A072290 A213691 A112127
Adjacent sequences: A158506 A158507 A158508 * A158510 A158511 A158512
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)hotmail.com), Mar 20 2009
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STATUS
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approved
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