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Search: id:A091997
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| A091997 |
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Numbers n such that 3*2^(n-1) - 1 is prime. |
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+0
1
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| 1, 2, 3, 4, 5, 7, 8, 12, 19, 35, 39, 44, 56, 65, 77, 95, 104, 144, 207, 217, 307, 325, 392, 459, 471, 828, 1275, 3277, 4205, 5135, 7560
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Eric Weisstein's World of Mathematics, Thabit ibn Kurrah's rules
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EXAMPLE
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3*2^(3-1) - 1 = 11 so a(1)=3
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MATHEMATICA
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Do[If[PrimeQ[3*2^(n - 1) - 1], Print[n]], {n, 1, 8000}] - Mohammed Bouayoun (Mohammed.Bouayoun(AT)yahoo.fr), Apr 13 2006
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PROGRAM
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(PARI) for (i=1, 1000, if(isprime(3*2^(i-1)-1), print1(i, ", ")))
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CROSSREFS
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Sequence in context: A115649 A111795 A046098 this_sequence A124168 A054762 A039088
Adjacent sequences: A091994 A091995 A091996 this_sequence A091998 A091999 A092000
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KEYWORD
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nonn
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AUTHOR
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Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 17 2004
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EXTENSIONS
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More terms from Mohammed Bouayoun (Mohammed.Bouayoun(AT)yahoo.fr), Apr 13 2006
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