A250744 Denominator of the harmonic mean of the first n positive Fibonacci numbers.
1, 1, 5, 17, 91, 379, 721, 35849, 614893, 6800951, 607326679, 3651532639, 851897554247, 24724573280923, 301787157353771, 14188276949397301, 22662903194758542865, 430644772287132696121, 1800653989272587268758525, 369150309888695460837999593
Offset: 1
Examples
a(4) = 17 because the first 4 positive Fibonacci numbers are [1,1,2,3], and 4/(1/1+1/1+1/2+1/3) = 24/17.
Links
- Colin Barker, Table of n, a(n) for n = 1..120
Programs
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Mathematica
Module[{nn=20,f},f=Fibonacci[Range[nn]];Table[HarmonicMean[Take[f,n]],{n,nn}]]//Denominator (* Harvey P. Dale, Aug 31 2020 *) -
PARI
s=vector(30); f=Vec(x/(1-x-x^2)+O(x^(#s+1))); n=d=0; for(k=1, #s, n++; d+=1/f[k]; s[k]=denominator(n/d)); s
Comments