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 A024920 a(n) = Sum_{k=1..n} (n-k) * floor(n/k). 1
 0, 2, 7, 17, 29, 51, 71, 104, 138, 183, 220, 293, 340, 409, 486, 580, 646, 767, 843, 981, 1099, 1221, 1317, 1525, 1653, 1802, 1961, 2168, 2297, 2568, 2709, 2951, 3154, 3359, 3578, 3942, 4118, 4352, 4598, 4978, 5176, 5576, 5786, 6136, 6504, 6798, 7030, 7574, 7862, 8270, 8609 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 FORMULA From Vaclav Kotesovec, May 28 2021: (Start) a(n) = n*A006218(n) - A024916(n). a(n) ~ n^2 * (log(n) + 2*gamma - 1 - Pi^2/12), where gamma is the Euler-Mascheroni constant A001620. (End) MAPLE A024920:=n->add((n-k)*floor(n/k), k=1..n): seq(A024920(n), n=1..80); # Wesley Ivan Hurt, Apr 02 2017 MATHEMATICA Table[Sum [(n - k) Floor[n/k], {k, n}], {n, 51}] (* Michael De Vlieger, Apr 03 2017 *) Table[Sum[n*DivisorSigma[0, k] - DivisorSigma[1, k], {k, 1, n}], {n, 1, 50}] (* Vaclav Kotesovec, May 28 2021 *) PROG (PARI) a(n) = sum(k=1, n, (n-k)*floor(n/k)) \\ Michel Marcus, Mar 23 2013 CROSSREFS Sequence in context: A260801 A031377 A019357 * A091313 A049554 A019398 Adjacent sequences: A024917 A024918 A024919 * A024921 A024922 A024923 KEYWORD nonn AUTHOR Clark Kimberling STATUS approved

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Last modified June 4 23:50 EDT 2023. Contains 363130 sequences. (Running on oeis4.)