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Search: id:A101636
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| A101636 |
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a(n)=least odd prime p such that (p^(P(n))-1)/(p-1) is prime with P(i)=i-th prime, n>1. |
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1
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| 3, 7, 3, 5, 3, 11, 11, 113, 151, 19, 61, 53, 89, 5, 307, 19, 19, 491, 3, 11, 271, 41, 251, 271, 359, 3, 19, 79, 233, 5, 7, 13, 11, 5, 29, 71, 139, 127, 139, 2003, 5, 743, 673, 593, 383, 653, 661, 251, 6389, 2833, 223, 163, 37, 709, 131, 41, 2203, 941, 2707, 13, 1283
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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All primes certified using PRIMO.
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EXAMPLE
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(3^3-1)/2=26/2=13 prime so for P(2) a(2)=3.
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MATHEMATICA
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a = {}; Do[ p1 = Prime[n]; k = 2; While[p2 = Prime[k]; ! PrimeQ[(p2^p1 - 1)/(p2 - 1)], k++ ]; AppendTo[a, p2]; , {n, 2, 62}]; a (Ray Chandler, Jan 27 2005)
f[n_] := Block[{P = Prime[n], k = 2}, While[p = Prime[k]; !PrimeQ[(p^P - 1)/(p - 1)], k++ ]; Prime[ k]]; Table[ f[n], {n, 2, 62}] (from Robert G. Wilson v Jan 27 2005)
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CROSSREFS
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Sequence in context: A111383 A021968 A132821 this_sequence A096247 A122583 A001265
Adjacent sequences: A101633 A101634 A101635 this_sequence A101637 A101638 A101639
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KEYWORD
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nonn
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AUTHOR
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Pierre CAMI (pierrecami(AT)tele2.fr), Jan 26 2005
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 27 2005
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