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Search: id:A112861
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| A112861 |
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Numbers n such that (2*n)!/(2*(n!)^2)-1 is prime. |
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+0
7
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| 2, 6, 10, 21, 45, 63, 306, 404, 437, 471, 646, 1174, 1192, 1334, 1975, 2397, 2410, 4305, 6111, 7852, 9488
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The next term is > 11000.
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MATHEMATICA
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lst={}; Do[If[PrimeQ[(2*n)!/(2*(n!)^2)-1], AppendTo[lst, n]], {n, 10^3}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 10 2008]
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CROSSREFS
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Cf. A001700(n-1)=(2*n)!/(2*(n!)^2), A112862 primes of the form (2*n)!/(2*(n!)^2)-1, A112853 (2*n)!/n!-1 is prime, A112855 (2*n)!/n!+1 is prime, A066726 (2*n)!/(n!)^2-1 is prime, A112859 (2*n)!/(n!)^2+1 is prime, A112863 (2*n)!/(2*(n!)^2)+1 is prime.
Sequence in context: A083176 A103628 A034450 this_sequence A140775 A077064 A080715
Adjacent sequences: A112858 A112859 A112860 this_sequence A112862 A112863 A112864
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KEYWORD
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hard,nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), Sep 30 2005
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