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A175172
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Primes p such that 3*2^p+1 is also prime.
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2
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..4.
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FORMULA
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A000040 INTERSECT A002253. - R. J. Mathar, Jan 04 2011
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EXAMPLE
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For p=2, 3*2^2+1=13; p=5. 3*2^5+1=97; p=41, 3*2^41+1=6597069766657.
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MAPLE
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select(p->isprime(p) and isprime(3*2^p+1), [$0..5000]); # Muniru A Asiru, Dec 19 2018
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MATHEMATICA
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Select[Prime[Range[1000]], PrimeQ[3 2^# + 1] &] (* Vincenzo Librandi, Dec 19 2018 *)
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PROG
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(MAGMA) [p: p in PrimesUpTo(4000) | IsPrime(3*2^p+1)]
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CROSSREFS
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Cf. A000040, A002253.
Sequence in context: A185052 A088547 A009457 * A218057 A126469 A054859
Adjacent sequences: A175169 A175170 A175171 * A175173 A175174 A175175
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KEYWORD
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nonn,more
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AUTHOR
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Vincenzo Librandi, Mar 09 2010
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STATUS
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approved
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