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A319756
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Expansion of Product_{k>=1} (1 - x^k)/(1 - k*x^k).
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1
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1, 0, 1, 2, 5, 6, 18, 20, 52, 76, 151, 214, 486, 638, 1265, 1990, 3572, 5288, 9968, 14568, 26270, 40246, 68326, 104414, 182191, 271892, 457636, 708012, 1164554, 1774422, 2945077, 4450020, 7261298, 11138514, 17827308, 27228060, 43860232, 66305840, 105486224, 161284674, 253846152
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OFFSET
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0,4
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COMMENTS
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LINKS
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FORMULA
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G.f.: exp(Sum_{k>=1} ( Sum_{d|k} d*(d^(k/d) - 1) ) * x^k/k).
a(n) ~ c * 3^(n/3), where
c = 4613.026226899587659466790384528262900057997961519... if mod(n,3)=0
c = 4612.491093385908314202944836907761153110706939289... if mod(n,3)=1
c = 4612.543916007416515763773288072302642108310934844... if mod(n,3)=2
(End)
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MAPLE
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a:=series(mul((1-x^k)/(1-k*x^k), k=1..100), x=0, 41): seq(coeff(a, x, n), n=0..40); # Paolo P. Lava, Apr 02 2019
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MATHEMATICA
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nmax = 40; CoefficientList[Series[Product[(1 - x^k)/(1 - k*x^k), {k, 1, nmax}], {x, 0, nmax}], x]
nmax = 40; CoefficientList[Series[Exp[Sum[Sum[d (d^(k/d) - 1), {d, Divisors[k]}] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x]
a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d (d^(k/d) - 1), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 40}]
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PROG
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(PARI) x='x+O('x^40); Vec(prod(n=1, 40, (1-x^n)/(1-n*x^n))) \\ Altug Alkan, Sep 27 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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