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A084406
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Numbers k such that k#*2^k-1 is prime, where k# = product of primes <= k.
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1
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2, 3, 7, 8, 14, 16, 18, 20, 40, 42, 44, 53, 134, 154, 185, 187, 191, 197, 200, 201, 230, 235, 239, 244, 256, 282, 303, 358, 489, 536, 665, 684, 719, 1098, 1204, 1400, 1516, 1629, 1903, 1997, 1999, 2104, 2477, 3075, 3676, 3785, 4115, 5429, 5808, 6069, 6276, 9095
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OFFSET
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1,1
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COMMENTS
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The values corresponding to terms 1098 through 1516 have been proved to be prime.
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LINKS
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MATHEMATICA
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p = 1; Do[If[PrimeQ[n], p *= n]; If[PrimeQ[p*2^n - 1], Print[n]], {n, 2, 10000}] (* Ryan Propper, Sep 05 2005 *)
Select[Table[{k, Times@@Prime[Range[PrimePi[k]]]}, {k, 720}], PrimeQ[#[[2]]2^#[[1]]-1]&][[;; , 1]] (* The program generates the first 33 terms of the sequence. *) (* Harvey P. Dale, Jan 20 2024 *)
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CROSSREFS
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KEYWORD
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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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