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Search: id:A124417
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| A124417 |
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a(n) = least k such that 2^i*k+1 is prime for 1<=i<=n. |
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+0
7
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| 1, 1, 9, 765, 765, 8325, 8325, 7757430, 428547690, 102764221560
(list; graph; listen)
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OFFSET
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1,3
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MATHEMATICA
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k = 1; Do[If[n < 3, inc = 1, If[n == 3, inc = 3, inc = 15]; ]; If[Mod[k, inc] > 0, k = k + inc - Mod[k, inc]]; While[Nand @@ PrimeQ[Table[2^j, {j, n}]*k + 1], k += inc]; Print[k], {n, 1, 15}] (*Chandler*)
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CROSSREFS
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Cf. A005097, A123998, A124041, A124412-A124416.
Sequence in context: A122251 A015481 A145183 this_sequence A159356 A091057 A137065
Adjacent sequences: A124414 A124415 A124416 this_sequence A124418 A124419 A124420
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KEYWORD
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nonn,more
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Nov 02 2006
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EXTENSIONS
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Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 21 2006
a(10) from Farideh Firoozbakht, Nov 25 2006
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