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A071576
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a(n) = least k such that 2ik+1 is prime for all 1<=i<=n.
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10
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1, 1, 1, 165, 5415, 12705, 256410, 256410, 6480303060, 217245863835, 946622690475, 35511547806735, 439116128090640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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MATHEMATICA
| k = 1; Do[ While[p = Table[2*i*k + 1, {i, 1, n}]; Union[ PrimeQ[p]] != {True}, k++ ]; Print[k], {n, 1, 15}] (Robert G. Wilson v)
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PROG
| (PARI) for(n=1, 6, s=1; while(sum(i=1, n, isprime(2*s*i+1))<n, s++); print1(s, ", "))
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CROSSREFS
| Cf. A088250, A124516, A124522, A124522, A063983.
Cf. A005097, A123998, A124408-A124411.
Sequence in context: A145055 A194483 A105944 * A140912 A132055 A046178
Adjacent sequences: A071573 A071574 A071575 * A071577 A071578 A071579
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KEYWORD
| more,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), May 31 2002
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EXTENSIONS
| Extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 06 2002
a(9) from Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
a(10)-a(13) from Don Reble (djr(AT)nk.ca), Nov 05 2006
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