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Search: id:A117587
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| A117587 |
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Numbers n such that 2^prime(n) - prime(n)^2 is prime. |
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+0
1
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| 3, 4, 7, 8, 16, 23, 49, 89, 331, 497, 1122, 11222
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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No more terms below 5000. -Giovanni Resta (g.resta(AT)iit.cnr.it), Apr 03 2006
p is a prime element of the sequence A072180 iff pi(p) is a term of A117587. So since 119087 is a prime term of A072180, pi(119087)= 11222 is in the sequence. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 08 2006
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EXAMPLE
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4 is in the sequence because the 4th prime is 7 and 2^7-7^2=79 is a prime.
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MAPLE
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a:=proc(n) if isprime(2^ithprime(n)-ithprime(n)^2)=true then n else fi end: seq(a(n), n=1..400); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 06 2006
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PROGRAM
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(PARI) for(i=1, 100, if(isprime(2^prime(i)-prime(i)^2), print1(i, ", ")))
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CROSSREFS
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Cf. A072180.
Sequence in context: A112062 A037013 A050069 this_sequence A130420 A101715 A075773
Adjacent sequences: A117584 A117585 A117586 this_sequence A117588 A117589 A117590
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KEYWORD
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hard,more,nonn
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AUTHOR
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Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 03 2006
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EXTENSIONS
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3 more terms from Giovanni Resta (g.resta(AT)iit.cnr.it), Apr 03 2006
One more term from Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 08 2006
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