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A092913
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a(0) = 1; a(n) = least multiple of a(n-1) such that every k with a(n)-n <= k <= a(n) + n is composite. The least distance of a prime on either side from a(n) is >n.
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0
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1, 9, 117, 117, 1404, 5616, 5616, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 3246048, 3246048, 38952576, 38952576, 38952576, 38952576, 38952576, 38952576
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OFFSET
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0,2
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LINKS
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EXAMPLE
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a(2) = a(3) = 117 = 9*13 and all the numbers from 117-2 = 115 to 117+2 = 119 are
composite.
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MATHEMATICA
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f[s_] := Block[{k, n, inc}, n = Length[s]; k = inc = Last[s]; While[Or @@ PrimeQ /@ Range[k - n, k + n], k += inc]; Append[s, k]]; Nest[f, {1}, 30] (* Ray Chandler, Sep 23 2006 *)
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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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