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A024921
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a(n) = Sum_{k=1..n} floor((n/k)*floor(n/k)).
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1
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1, 5, 11, 22, 33, 52, 67, 93, 117, 149, 174, 219, 250, 293, 339, 392, 434, 500, 546, 619, 680, 748, 804, 903, 969, 1051, 1131, 1230, 1301, 1422, 1497, 1609, 1708, 1814, 1915, 2062, 2156, 2275, 2388, 2543, 2646, 2808, 2915, 3070, 3219, 3359, 3480, 3683, 3813, 3985, 4137
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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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a(n) = n^2*Pi^2/6 + O(n*log n) as n -> infinity. - Robert Israel, Aug 05 2016
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MAPLE
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f:= n -> add(floor(n/k*floor(n/k)), k=1..n):
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MATHEMATICA
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Table[Sum[Floor[(n / k) Floor[n / k]], {k, 1, n}], {n, 1, 50}] (* Vincenzo Librandi, Jul 28 2019 *)
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PROG
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(PARI) a(n) = sum(k=1, n, floor((n/k)*floor(n/k))) \\ Michel Marcus, Mar 23 2013
(Magma) [&+[(n div k)*(n div k): k in [1..n]]: n in [1..60]]; // Vincenzo Librandi, Jul 28 2019
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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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