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Search: id:A137288
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| A137288 |
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Numbers n such that 2*p(n)-1 is prime, where p(n) is the n-th prime. |
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+0
1
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| 1, 2, 4, 8, 11, 12, 22, 25, 34, 37, 46, 47, 50, 58, 63, 67, 68, 73, 75, 85, 95, 101, 106, 110, 111, 114, 121, 125, 129, 141, 145, 151, 159, 163, 168, 169, 180, 193, 203, 207, 211, 222, 226, 232, 242, 254, 258, 260, 274, 285
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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n=11 : 2*p(11)-1 = 2* 31-1 = 61 is prime, n=11 belongs to the sequence.
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MAPLE
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P:=proc(n) local a, i; for i from 1 by 1 to n do a:=2*ithprime(i)-1; if isprime(a) then print(i); fi; od; end: P(301); - Paolo P. Lava (ppl(AT)spl.at), Apr 15 2008
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CROSSREFS
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Cf. A000040.
Adjacent sequences: A137285 A137286 A137287 this_sequence A137289 A137290 A137291
Sequence in context: A028846 A080152 A136994 this_sequence A116443 A078649 A022442
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KEYWORD
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easy,nonn
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AUTHOR
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Ctibor O. Zizka (ctibor.zizka(AT)seznam.cz), Apr 05 2008
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EXTENSIONS
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More terms from Paolo P. Lava (ppl(AT)spl.at), Apr 15 2008
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