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A097099
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Least k such that (2^k)*P(n)# - 1 is prime, where P(i)=i-th prime and P(i)# =i-th primorial.
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1
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1, 1, 1, 1, 2, 6, 1, 1, 2, 3, 12, 1, 2, 22, 2, 4, 13, 12, 6, 1, 4, 1, 4, 9, 2, 9, 5, 6, 2, 1, 9, 17, 22, 7, 19, 73, 23, 12, 5, 27, 33, 64, 33, 5, 7, 41, 44, 35, 29, 3, 19, 6, 26, 5, 11, 9, 33, 34, 16, 63, 46, 8, 4, 24, 48, 32, 11, 29, 26, 6, 25, 17, 31, 6, 46, 33, 46, 17, 8, 61, 12, 23, 76
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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MATHEMATICA
| f[n_] := Block[{k = 1, p = Product[Prime[i], {i, n}]}, While[ !PrimeQ[2^k*p - 1], k++ ]; k]; Table[ f[n], {n, 83}] (* from Robert G. Wilson v Sep 27 2004 *)
kp[n_]:=Module[{k=1}, While[!PrimeQ[2^k n-1], k++]; k]; With[{prmrls=Rest[ FoldList[Times, 1, Prime[Range[90]]]]}, kp/@prmrls] (* From Harvey P. Dale, Feb 01 2012 *)
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CROSSREFS
| Sequence in context: A127508 A090185 A059813 * A197111 A065529 A205015
Adjacent sequences: A097096 A097097 A097098 * A097100 A097101 A097102
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KEYWORD
| nonn,changed
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AUTHOR
| Pierre CAMI (pierre-cami(AT)bbox.fr), Sep 15 2004
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 27 2004
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