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A098571
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a(n) is the least k such that Mersenne-prime(n)*prime(k)# + 1 is prime, where prime(k)# is the k-th primorial.
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1
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1, 2, 6, 6, 16, 5, 3, 4, 5, 33, 29, 24, 31, 124, 290, 103, 370, 186, 4654, 133, 221, 244, 206, 726, 601, 18
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..26.
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MATHEMATICA
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f[p_] := Module[{k = 1, q = r = 2}, While[! PrimeQ[r*p + 1], q = NextPrime[q]; r *= q; k++]; k]; f /@ (2^MersennePrimeExponent[Range[15]] - 1) (* Amiram Eldar, Aug 28 2021 *)
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CROSSREFS
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Cf. A000043, A000668, A002110, A098570.
Sequence in context: A316785 A056136 A349288 * A194120 A161503 A019076
Adjacent sequences: A098568 A098569 A098570 * A098572 A098573 A098574
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KEYWORD
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nonn,more
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AUTHOR
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Pierre CAMI, Sep 16 2004
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EXTENSIONS
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a(19)-a(26) from Amiram Eldar, Aug 28 2021
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STATUS
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approved
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