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 A338683 a(n) = - Sum_{d|n} (-n/d)^d * binomial(d+n/d-1, d). 3
 1, 3, 10, 3, 26, 13, 50, -177, 352, -84, 122, -996, 170, -153, 9704, -13313, 290, -6518, 362, -2771, 107986, 17073, 530, -805070, 394376, 99984, 1203580, 1196313, 842, -4500745, 962, -13313025, 14199222, 2316234, 33547310, -19898071, 1370, 10418613, 168405072 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA G.f.: Sum_{k >= 1} (1 - 1/(1 + k * x^k)^k). If p is prime, a(p) = (-1)^(p-1) + p^2. MATHEMATICA a[n_] := -DivisorSum[n, (-n/#)^# * Binomial[# + n/# - 1, #] &]; Array[a, 40] (* Amiram Eldar, Apr 24 2021 *) PROG (PARI) a(n) = -sumdiv(n, d, (-n/d)^d*binomial(d+n/d-1, d)); (PARI) N=66; x='x+O('x^N); Vec(sum(k=1, N, 1-1/(1+k*x^k)^k)) CROSSREFS Cf. A327238, A338662, A338682, A338684, A338688. Sequence in context: A010708 A072988 A170855 * A320583 A339317 A131814 Adjacent sequences:  A338680 A338681 A338682 * A338684 A338685 A338686 KEYWORD sign AUTHOR Seiichi Manyama, Apr 23 2021 STATUS approved

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Last modified August 17 15:14 EDT 2022. Contains 356189 sequences. (Running on oeis4.)