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A091513
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Numbers k such that (2^k + 1)^2 - 2 = 4^k + 2^(k+1) - 1 is prime.
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10
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0, 1, 2, 3, 5, 8, 9, 12, 15, 17, 18, 21, 23, 27, 32, 51, 65, 87, 180, 242, 467, 491, 501, 507, 555, 591, 680, 800, 1070, 1650, 2813, 3281, 4217, 5153, 6287, 6365, 10088, 10367, 37035, 45873, 69312, 102435, 106380, 108888, 110615, 281621, 369581, 376050, 442052, 621443, 661478
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OFFSET
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1,3
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LINKS
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FORMULA
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MATHEMATICA
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Flatten[Position[Table[(2^n + 1)^2 - 2, {n, 0, 10^3}], _?PrimeQ] - 1] (* Eric W. Weisstein, Feb 10 2016 *)
Select[Range[0, 5000], PrimeQ[(2^# + 1)^2 - 2] & ] (* Vincenzo Librandi, Feb 19 2016 *)
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PROG
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CROSSREFS
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Cf. A091514 (primes of the form (2^n + 1)^2 - 2).
Cf. A093069 (numbers of the form (2^n + 1)^2 - 2).
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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a(46) from Cletus Emmanuel (cemmanu(AT)yahoo.com), Oct 07 2005
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STATUS
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approved
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