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 A325211 a(1) = 1; a(n) = Sum_{d|n, d
 1, 2, 2, 7, 2, 12, 2, 24, 7, 12, 2, 58, 2, 12, 12, 82, 2, 58, 2, 58, 12, 12, 2, 256, 7, 12, 24, 58, 2, 104, 2, 280, 12, 12, 12, 355, 2, 12, 12, 256, 2, 104, 2, 58, 58, 12, 2, 1072, 7, 58, 12, 58, 2, 256, 12, 256, 12, 12, 2, 652, 2, 12, 58, 956, 12, 104, 2, 58, 12, 104 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA G.f. A(x) satisfies: A(x) = x + Sum_{k>=2} tau(k) * A(x^k). a(p) = 2, where p is prime. MATHEMATICA a[n_] := If[n == 1, n, Sum[If[d < n, DivisorSigma[0, n/d] a[d], 0], {d, Divisors[n]}]]; Table[a[n], {n, 1, 70}] nmax = 70; A[_] = 0; Do[A[x_] = x + Sum[DivisorSigma[0, k] A[x^k], {k, 2, nmax}] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x] // Rest PROG (PARI) seq(n)={my(v=vector(n)); v[1]=1; for(n=2, #v, v[n] = sumdiv(n, d, v[d]*numdiv(n/d))); v} \\ Andrew Howroyd, Sep 05 2019 CROSSREFS Cf. A000005, A007427, A007557, A325212. Sequence in context: A021444 A029632 A089588 * A211780 A014840 A218756 Adjacent sequences:  A325208 A325209 A325210 * A325212 A325213 A325214 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Sep 05 2019 STATUS approved

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Last modified April 6 14:08 EDT 2020. Contains 333276 sequences. (Running on oeis4.)