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 A308696 a(n) = Sum_{d|n} d^(2*d). 6
 1, 17, 730, 65553, 9765626, 2176783082, 678223072850, 281474976776209, 150094635296999851, 100000000000009765642, 81402749386839761113322, 79496847203390846310290154, 91733330193268616658399616010, 123476695691247935826908004929122 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..214 FORMULA L.g.f.: -log(Product_{k>=1} (1 - x^k)^(k^(2*k-1))) = Sum_{k>=1} a(k)*x^k/k. G.f.: Sum_{k>=1} k^(2*k) * x^k/(1 - x^k). MATHEMATICA a[n_] := DivisorSum[n, #^(2*#) &]; Array[a, 14] (* Amiram Eldar, May 09 2021 *) PROG (PARI) {a(n) = sumdiv(n, d, d^(2*d))} (PARI) N=20; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-x^k)^k^(2*k-1))))) (PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, k^(2*k)*x^k/(1-x^k))) CROSSREFS Column k=2 of A308698. Cf. A073705, A308753, A308756. Sequence in context: A128274 A012085 A298306 * A308594 A308570 A218423 Adjacent sequences: A308693 A308694 A308695 * A308697 A308698 A308699 KEYWORD nonn AUTHOR Seiichi Manyama, Jun 17 2019 STATUS approved

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Last modified June 13 00:51 EDT 2024. Contains 373362 sequences. (Running on oeis4.)