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 A308313 a(n) = Sum_{k=1..n} (-1)^(n-k) * k^n * floor(n/k). 1
 1, 2, 22, 203, 2285, 33855, 609345, 12420372, 284964519, 7347342215, 209807114169, 6554034238459, 222469737401739, 8159109186320903, 321461264348047819, 13538455640979049698, 606976994365011212414, 28864017965496692865925, 1451086990386146504580735, 76896033641977171208887465 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) = [x^n] (1/(1 + x)) * Sum_{k>=1} k^n * x^k/(1 - (-x)^k). a(n) = Sum_{k=1..n} Sum_{d|k} (-1)^(n-d) * d^n. a(n) ~ c * n^n, where c = 1/(1 + exp(-1)) = 0.7310585786300048792511592418218362743651446401650565192763659... - Vaclav Kotesovec, Aug 22 2019, updated Jul 19 2021 MATHEMATICA Table[Sum[(-1)^(n - k) k^n Floor[n/k] , {k, 1, n}], {n, 1, 20}] Table[SeriesCoefficient[1/(1 + x) Sum[k^n x^k/(1 - (-x)^k), {k, 1, n}], {x, 0, n}], {n, 1, 20}] Table[(-1)^n Sum[DivisorSigma[n, k] - 2 Total[Select[Divisors[k], OddQ]^n], {k, 1, n}], {n, 1, 20}] PROG (PARI) a(n)={sum(k=1, n, (-1)^(n-k) * k^n * (n\k))} \\ Andrew Howroyd, Aug 22 2019 CROSSREFS Cf. A319194. Sequence in context: A043037 A058441 A255043 * A304024 A239688 A350965 Adjacent sequences:  A308310 A308311 A308312 * A308314 A308315 A308316 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Aug 22 2019 STATUS approved

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Last modified May 28 08:23 EDT 2022. Contains 354112 sequences. (Running on oeis4.)