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A059959
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Distance of 2^n from its nearest prime neighbor and in case of a tie, choose the smaller.
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3
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-1, 0, 1, 1, -1, 1, 3, 1, -1, 3, 3, -5, 3, 1, 3, -3, -1, 1, -3, 1, 3, 9, 3, -9, 3, -35, 5, -29, -3, 3, -3, 1, 5, 9, -25, 31, 5, -9, -7, 7, -15, 21, 11, -29, -7, 55, -15, -5, -21, -69, 27, -21, -21, -5, 33, -3, 5, -9, 27, 55, -33, 1, 57, 25, -13, 49, 5, -3, 23, 19, -25, -11, -15, -29, 35, -33, 15, -11, -7, -23, -13, -17, -9, 55, -3, 19
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,7
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FORMULA
| a(n) = A000079(n)-A117387(n).
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EXAMPLE
| n=19, 2^19=524288, prevprime(524288)=524287, nextprime(524288)=524309, so min{21,1}=1=a(19)
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MAPLE
| with(numtheory): [seq(min(nextprime(2^i)-2^i, 2^i-prevprime(2^i)), i=2..100)];
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MATHEMATICA
| f[n_] := Block[{k = 0}, While[ !PrimeQ[2^n - k] && !PrimeQ[2^n + k], k++ ]; Min@Select[{2^n - k, 2^n + k}, PrimeQ@# &]]; Table[2^n - f[n], {n, 0, 85}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Mar 14 2006)
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CROSSREFS
| Cf. A013597, A013603, A014210, A014234, A058249.
Sequence in context: A060592 A080426 A133116 * A192812 A051120 A114476
Adjacent sequences: A059956 A059957 A059958 * A059960 A059961 A059962
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KEYWORD
| sign
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Mar 02 2001
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EXTENSIONS
| Signs added by Robert G. Wilson v (rgwv(at)rgwv.com), Mar 14 2006
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