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A249950 Numerator of the harmonic mean of the first n cubes. 2

%I #9 Aug 20 2017 12:17:34

%S 1,16,648,6912,1080000,144000,57624000,526848000,144027072000,

%T 160030080000,234300040128000,255600043776000,608349404190528000,

%U 655145512205184000,701941620219840000,5989901825875968000,31267661899936670208000,3678548458816078848000

%N Numerator of the harmonic mean of the first n cubes.

%C A007408 contains the corresponding denominators.

%H Colin Barker, <a href="/A249950/b249950.txt">Table of n, a(n) for n = 1..750</a>

%e a(3) = 648 because the first 3 cubes are [1,8,27] and 3 / (1/1+1/8+1/27) = 648/251.

%t Table[Numerator[n/Sum[1/k^3,{k,1,n}]],{n,1,20}] (* _Vaclav Kotesovec_, Nov 14 2014 *)

%t Table[Numerator[HarmonicMean[Range[n]^3]],{n,20}] (* _Harvey P. Dale_, Aug 20 2017 *)

%o (PARI)

%o harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])

%o s=vector(30); for(k=1, #s, s[k]=numerator(harmonicmean(vector(k, i, i^3)))); s

%Y Cf. A007408.

%K nonn

%O 1,2

%A _Colin Barker_, Nov 13 2014

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Last modified March 29 01:36 EDT 2024. Contains 371264 sequences. (Running on oeis4.)