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A131119
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a(n) = (-1)^n * Sum_{i=1..floor(n/2)} i * floor(n/(n-i)).
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1
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0, 0, 2, -1, 5, -3, 9, -6, 14, -10, 20, -15, 27, -21, 35, -28, 44, -36, 54, -45, 65, -55, 77, -66, 90, -78, 104, -91, 119, -105, 135, -120, 152, -136, 170, -153, 189, -171, 209, -190, 230, -210, 252, -231, 275, -253, 299, -276, 324, -300, 350, -325, 377, -351, 405
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OFFSET
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0,3
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COMMENTS
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LINKS
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MATHEMATICA
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Table[(-1)^n*Sum[i*Floor[n/(n - i)], {i, Floor[n/2]}], {n, 0, 80}] (* Wesley Ivan Hurt, Nov 26 2020 *)
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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