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A144069
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Euler transform of powers of 5.
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4
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1, 5, 40, 285, 2020, 13876, 93885, 624480, 4100470, 26609290, 170940381, 1088260190, 6872684570, 43088845030, 268374618310, 1661512492031, 10229763359245, 62663268647185, 382039881168240, 2318974249801205, 14018511922088296, 84418983571948025
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: Product_{j>0} 1/(1-x^j)^(5^j).
a(n) ~ 5^n * exp(2*sqrt(n) - 1/2 + c) / (2 * sqrt(Pi) * n^(3/4)), where c = Sum_{m>=2} 1/(m*(5^(m-1)-1)) = 0.1412899716579209220312645657307029151422082... . - Vaclav Kotesovec, Mar 14 2015
G.f.: exp(5*Sum_{k>=1} x^k/(k*(1 - 5*x^k))). - Ilya Gutkovskiy, Nov 09 2018
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MAPLE
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with(numtheory): etr:= proc(p) local b; b:=proc(n) option remember; `if`(n=0, 1, add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n)/n) end end: a:=n-> etr(j->5^j)(n): seq(a(n), n=0..40);
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MATHEMATICA
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etr[p_] := Module[{b}, b[n_] := b[n] = If[n == 0, 1, Sum[Sum[d*p[d], {d, Divisors[j]}]*b[n - j], {j, 1, n}]/n]; b]; a[n_] := etr[Function[5^#]][n]; Table[ a[n], {n, 0, 40}] (* Jean-François Alcover, Mar 09 2015, after Alois P. Heinz *)
CoefficientList[Series[Product[1/(1-x^k)^(5^k), {k, 1, 30}], {x, 0, 30}], x] (* G. C. Greubel, Nov 09 2018 *)
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PROG
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(PARI) m=30; x='x+O('x^m); Vec(prod(k=1, m, 1/(1-x^k)^(5^k))) \\ G. C. Greubel, Nov 09 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!( (&*[1/(1-x^k)^(5^k): k in [1..m]]) )); // G. C. Greubel, Nov 09 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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