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Numerator of the contraharmonic mean of the first n primes.
1

%I #6 Dec 07 2017 19:16:06

%S 2,13,19,87,52,377,333,1027,389,799,1679,4727,3204,8257,5233,4425,

%T 4189,20477,12483,30007,4417,41577,24233,56387,16449,75997,43303,

%U 32685,13742,122705,69417,155995,43691,64695,108143,239087,32967,290305,159097,116041

%N Numerator of the contraharmonic mean of the first n primes.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Contraharmonic_mean"> Contraharmonic mean</a>.

%F a(n) = numerator( Sum_{k=1..n} prime(k)^2/Sum_{k=1..n} prime(k) ).

%F a(n) = numerator( A024450(n)/A007504(n) ).

%t a[n_]:=ContraharmonicMean[Prime[Range[n]]];

%t nmax=40;

%t at=Table[a[n],{n,1,nmax}];

%t Numerator[at]

%Y Cf. A007504 (sum of the first n primes), A024450 (sum of squares of the first n primes), A294612 (denominators).

%K nonn,frac

%O 1,1

%A _Andres Cicuttin_, Dec 07 2017