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A249446
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Numbers n such that 2*(n^2-1) - 1 and 2*(n^2-1) + 1 are primes.
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3
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2, 4, 10, 11, 34, 41, 46, 49, 56, 59, 76, 85, 95, 125, 160, 181, 185, 196, 200, 206, 220, 245, 266, 280, 295, 301, 304, 346, 365, 379, 386, 391, 440, 470, 505, 556, 571, 595, 659, 679, 689, 731, 784, 815, 820, 854, 869, 896, 944, 959, 994, 1001, 1004, 1015, 1025, 1154, 1250, 1345, 1376
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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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2 is in this sequence because 2*(2^2-1) - 1 = 5 and 2*(2^2-1) + 1 = 7 are both prime.
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MAPLE
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select(n -> isprime(2*n^2-3) and isprime(2*n^2-1), [$1 .. 10000]); # Robert Israel, Nov 18 2014
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MATHEMATICA
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Select[Range[0, 1500], PrimeQ[2 #^2 - 3] && PrimeQ[2 #^2 - 1] &] (* Vincenzo Librandi, Oct 29 2014 *)
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PROG
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(Magma) [ n: n in [1..1400] | IsPrime(2*(n^2-1)-1) and IsPrime(2*(n^2-1)+1) ];
(PARI) isok(n) = isprime(2*(n^2-1) - 1) && isprime(2*(n^2-1) + 1); \\ Michel Marcus, Oct 31 2014
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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