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A128550
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a(n) = p, the lesser of twin primes (p,q=p+2) such that p*q+p+q is prime.
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3
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3, 5, 11, 17, 41, 59, 101, 137, 311, 419, 521, 809, 1019, 1049, 1151, 1229, 1319, 1427, 2111, 2237, 2267, 3119, 3329, 3371, 3539, 4001, 4049, 4091, 4217, 4421, 4721, 5009, 6359, 6569, 6689, 6761, 7487, 7949, 8537, 8627, 9629, 9719, 10007, 10091, 10709
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OFFSET
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1,1
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COMMENTS
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Or, primes p such that p+2 and 2 + 4*p + p^2 are prime.
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LINKS
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Table of n, a(n) for n=1..45.
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EXAMPLE
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3, 5 and 3*5+3+5=23 are prime; 5, 7 and 5*7+5+7=47 are prime; 11, 13 and 11*13+11+13 are primes.
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MATHEMATICA
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lst={}; Do[p=Prime[n]; r=p+2; If[PrimeQ[r], If[PrimeQ[p*r+p+r], AppendTo[lst, p]]], {n, 8!}]; lst [From Vladimir Joseph Stephan Orlovsky, Nov 28 2009]
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PROG
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(PARI) is(n)=isprime(n)&&isprime(n+2)&&isprime(n^2+4*n+2) \\ Charles R Greathouse IV, Jan 29 2013
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CROSSREFS
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Cf. A096342, A126148, A128547, A128548, A128551.
Sequence in context: A007455 A034729 A115786 * A096479 A129809 A208572
Adjacent sequences: A128547 A128548 A128549 * A128551 A128552 A128553
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov, Mar 10 2007
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STATUS
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approved
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