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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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11
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1, 1, 1, 165, 5415, 12705, 256410, 256410, 6480303060, 217245863835, 946622690475, 35511547806735, 439116128090640, 5714676453270219435
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OFFSET
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1,4
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LINKS
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MATHEMATICA
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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
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(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
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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