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A117587
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Numbers k such that 2^prime(k) - prime(k)^2 is prime.
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3
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3, 4, 7, 8, 16, 23, 49, 89, 331, 497, 1122, 11222
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OFFSET
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1,1
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COMMENTS
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LINKS
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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) then n else fi end: seq(a(n), n=1..400); # Emeric Deutsch, Apr 06 2006
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MATHEMATICA
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Select[Range[1200], PrimeQ[2^# - #^2] &@ Prime@ # &] (* Michael De Vlieger, Feb 02 2019 *)
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PROG
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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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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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STATUS
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approved
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