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A227126
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Primes p_i such that 2^(i+1) - p_i is also prime.
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4
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2, 3, 5, 11, 17, 167, 193, 197, 433, 4111, 9173, 42929, 95279, 98897, 139409, 142567, 228617, 329333, 344209, 791191, 829177
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OFFSET
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1,1
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COMMENTS
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The corresponding primes 2^(i + 1) - prime(i) are 2, 5, 11, 53, 239, 1099511627609, 35184372088639, ...
The prime indices i are 1, 2, 3, 5, 7, 39, 44, 45, 84, 566, 1137, ...
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LINKS
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EXAMPLE
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5 is a term because 5 is the 3rd prime, and 2^(3+1) - 5 = 16 - 5 = 11 which is a prime
11 is in the sequence because 11 = prime(5) and 2^(5 + 1) - 11 = 64 - 11 = 53 is a prime.
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MATHEMATICA
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p = 2; lst = {}; While[p < 850001, If[ PrimeQ[ 2^(PrimePi@ p +1) - p], AppendTo[lst, p]; Print@ p]; p = NextPrime@ p]; lst (* Robert G. Wilson v, Jul 09 2014 *)
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PROG
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(PARI) lista(nn) = {ip = 1; forprime(p=2, nn, if (isprime(2^(ip+1)-p), print1(p, ", ")); ip++; ); } \\ Michel Marcus, Jul 12 2014
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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