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A095991
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Numbers n such that f(k) * 2^n - 1 is prime, where f(j) = A070826(j) and k is the number of decimal digits of 2^n.
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0
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2, 3, 4, 6, 14, 17, 18, 23, 33, 43, 45, 53, 60, 70, 114, 141, 162, 178, 387, 657, 787, 951, 1517, 1882, 1999, 2423, 2722, 3635, 3636, 3893, 5021, 5631
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history;
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internal format)
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OFFSET
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1,1
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COMMENTS
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a(1) through a(32) have been proved to be prime with WinPFGW. a(32) has 7901 digits. No more terms up to 7300.
Results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019
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LINKS
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Table of n, a(n) for n=1..32.
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EXAMPLE
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a(5)=14 because 1155 * 2^14 - 1 = 18923519, a prime.
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MATHEMATICA
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Do[ If[ PrimeQ[ Product[ Prime[i], {i, Floor[ n / Log[2, 10] + 1]}] * 2^(n - 1) - 1], Print[n]], {n, 7300}] (* Robert G. Wilson v, Jul 23 2004 *)
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CROSSREFS
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Sequence in context: A038767 A188715 A174046 * A293714 A049911 A056712
Adjacent sequences: A095988 A095989 A095990 * A095992 A095993 A095994
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KEYWORD
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more,nonn,base
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AUTHOR
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Jason Earls, Jul 18 2004
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EXTENSIONS
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Edited by Robert G. Wilson v, Jul 23 2004
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STATUS
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approved
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