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A072666
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Numbers n such that prime(n) + prime(n+1) - 1 is prime.
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4
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2, 3, 4, 5, 6, 8, 10, 11, 13, 14, 18, 19, 21, 25, 30, 31, 36, 41, 43, 44, 46, 47, 48, 50, 52, 53, 58, 59, 60, 62, 63, 66, 68, 70, 73, 74, 75, 78, 79, 80, 81, 83, 85, 90, 93, 99, 100, 101, 106, 112, 114, 116, 117, 120, 124, 126, 127, 129, 130, 131, 132, 137, 138, 140, 145, 147, 149
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OFFSET
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1,1
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LINKS
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FORMULA
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MAPLE
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N:= 10^4: # to get all terms n such that prime(n+1) <= N
Primes:= select(isprime, [2, seq(2*i+1, i=1..floor(N/2))]):
PP:= Primes[1..-2]+Primes[2..-1]:
select(t -> isprime(PP[t]-1), [$1..nops(PP)]); # Robert Israel, Dec 11 2014
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MATHEMATICA
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Select[Range[200], PrimeQ[Prime[#]+Prime[#+1]-1] &] (* Harvey P. Dale, Dec 16 2010 *)
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PROG
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(Magma) [n: n in [1..200] | IsPrime(NthPrime(n) + NthPrime(n+1)-1)] // Vincenzo Librandi, Aug 26 2012
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Herman H. Rosenfeld (herm3(AT)pacbell.net), Aug 12 2002
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EXTENSIONS
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STATUS
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approved
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