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Search: id:A113878
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| A113878 |
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a(1)=0; a(n+1) is the least number > a(n) such that sum{k=1..n+1} 2^a(k) isn't composite. |
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+0
1
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| 0, 1, 2, 4, 7, 16, 53, 66, 207, 1752, 5041, 6310
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Base 2 logarithms of A073924.
a(13) > 50000 -- Don Reble
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MATHEMATICA
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a[1] = 0; a[n_] := a[n] = Block[{k = a[n - 1] + 1, s = Plus @@ (2^Array[a, n - 1])}, While[ !PrimeQ[s + 2^k], k++ ]; k]; Array[a, 12] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A073924, A080355, A080567, A113824.
Sequence in context: A137568 A010355 A134455 this_sequence A026775 A027238 A076894
Adjacent sequences: A113875 A113876 A113877 this_sequence A113879 A113880 A113881
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Jan 27 2006
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EXTENSIONS
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Edited by Don Reble (djr(AT)nk.ca), Feb 17 2006
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