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A178698
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Largest k<n such that 2*composite(n)=composite(n-k)+composite(n+k).
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1
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0, 1, 0, 3, 4, 5, 4, 6, 7, 4, 0, 2, 7, 0, 5, 13, 15, 16, 13, 9, 11, 15, 20, 21, 18, 19, 25, 17, 0, 2, 21, 0, 19, 23, 25, 29, 23, 27, 28, 29, 39, 23, 14, 16, 38, 39, 40, 37, 38, 39, 32, 0, 1, 29, 30, 31, 28, 29, 30, 23, 24, 25, 26, 35, 22, 23, 38, 39, 40, 50, 57, 43, 44, 54, 32
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OFFSET
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1,4
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LINKS
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EXAMPLE
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a(1)=0 because 2*composite(1)=composite(1-0)+composite(1+0)=4+4=8.
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MATHEMATICA
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Composite[n_Integer] := FixedPoint[n + PrimePi@# + 1 &, n + PrimePi@ n + 1]; f[n_] := Block[{k = n - 1, m = Composite@ n}, While[k > 0 && 2 m != Composite[n + k] + Composite[n - k], k--]; k]; Array[f, 75]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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