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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
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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| n=11 : 2*p(11)-1 = 2* 31-1 = 61 is prime, n=11 belongs to the sequence.
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MAPLE
| 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 (paoloplava(AT)gmail.com), Apr 15 2008
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CROSSREFS
| Cf. A000040.
Sequence in context: A028846 A080152 A136994 * A116443 A078649 A161607
Adjacent sequences: A137285 A137286 A137287 * A137289 A137290 A137291
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KEYWORD
| easy,nonn
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AUTHOR
| Ctibor O. Zizka (ctibor.zizka(AT)seznam.cz), Apr 05 2008
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EXTENSIONS
| More terms from Paolo P. Lava (paoloplava(AT)gmail.com), Apr 15 2008
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