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A145264
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a(n) is the positive integer such that Sum_{k>=0} floor(n/(a(n)+k)) = n, or 0 if there is no such positive integer.
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3
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1, 0, 0, 2, 2, 0, 0, 3, 0, 0, 0, 0, 0, 0, 5, 0, 0, 6, 6, 0, 0, 7, 7, 0, 0, 8, 0, 0, 0, 0, 0, 0, 10, 0, 0, 11, 11, 0, 0, 12, 12, 0, 0, 13, 0, 0, 0, 0, 0, 0, 15, 0, 0, 16, 16, 0, 0, 17, 17, 0, 0, 18, 0, 0, 0, 0, 0, 0, 20, 0, 0, 21, 21, 0, 0, 22, 22, 0, 0, 23, 0, 0, 0, 0, 0, 0, 25, 0, 0, 26, 26, 0, 0, 27, 27
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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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For n = 8: floor(8/3) + floor(8/4) + floor(8/5) + floor(8/6) + floor(8/7) + floor(8/8) = 2 + 2 + 1 + 1 + 1 + 1 = 8. So a(8) = 3. For n = 6: floor(6/2) + floor(6/3) + floor(6/4) + floor(6/5) + floor(6/6) = 3 + 2 + 1 + 1 + 1 = 8, which is > 6. But floor(6/3) + floor(6/4) + floor(6/5) + floor(6/6) = 2 + 1 + 1 + 1 = 5, which is < 6. So a(6) = 0, because there is no integer at which to start the sequence of denominators so that the sum is 6.
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MAPLE
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A145264 := proc(n) local a, k; for a from 1 to n do if add( floor(n/(a+k)), k=0..n-a) = n then RETURN(a) ; fi; od: RETURN(0) ; end: for n from 1 to 120 do printf("%d, ", A145264(n)) ; od: # R. J. Mathar, Oct 07 2008
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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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