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A290845
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a(1) = 1; a(n) = Sum_{k=1..n} a(ceiling((n-1)/k)).
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0
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1, 2, 4, 8, 14, 24, 36, 56, 78, 110, 148, 200, 254, 334, 416, 522, 644, 798, 954, 1162, 1372, 1640, 1934, 2284, 2636, 3090, 3556, 4106, 4694, 5394, 6096, 6972, 7850, 8882, 9972, 11220, 12500, 14048, 15598, 17360, 19208, 21346, 23486, 26016, 28548, 31436, 34478, 37874, 41272, 45246
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 1;
a(2) = a(ceiling(1/1)) + a(ceiling(1/2)) = a(1) + a(1) = 2;
a(3) = a(ceiling(2/1)) + a(ceiling(2/2)) + a(ceiling(2/3)) = a(2) + a(1) + a(1) = 4, etc.
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MATHEMATICA
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a[1] = 1; a[n_] := a[n] = Sum[a[Ceiling[(n - 1)/k]], {k, 1, n}]; Table[a[n], {n, 50}]
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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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