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Search: id:A053662
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| A053662 |
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Numbers n such that 2n+1 divides n!+1. |
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+0
3
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| 3, 5, 9, 21, 23, 33, 39, 51, 63, 65, 81, 89, 95, 99, 113, 131, 173, 183, 191, 209, 215, 221, 239, 245, 251, 261, 281, 285, 299, 303, 309, 315, 341, 345, 363, 369, 371, 393, 411, 419, 431, 443, 473, 495, 509, 525, 543, 545, 561, 575, 593, 645, 659, 683, 711
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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n+1 divides n!+1 gives primes-1 by Wilson's Theorem. For the present sequence, there are 309 terms below 5000, compared with 669 primes (.462). There are 553 terms below 10000, compared with 1229 primes (.450) - Ed Pegg Jr (ed(AT)mathpuzzle.com), Dec 05 2001
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MATHEMATICA
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Drop[Union[Table[If[IntegerQ[(n!+1)/(2n+1)], n], {n, 1, 1000}]], -1] - Ed Pegg Jr (ed(AT)mathpuzzle.com), Dec 05 2001
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CROSSREFS
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Cf. A005097, A053663, A006093.
Sequence in context: A107028 A066777 A065901 this_sequence A050355 A069927 A136401
Adjacent sequences: A053659 A053660 A053661 this_sequence A053663 A053664 A053665
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KEYWORD
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easy,nonn
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AUTHOR
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Chris K. Caldwell (caldwell(AT)utm.edu), Feb 16 2000
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