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A334746 Denominator of Sum_{k=1..n} 1/(prime(k) - 1)^2. 4

%I

%S 1,4,16,144,3600,1800,57600,518400,62726400,3073593600,614718720,

%T 614718720,3073593600,3073593600,1625931014400,274782341433600,

%U 231091949145657600,231091949145657600,231091949145657600,231091949145657600,77030649715219200

%N Denominator of Sum_{k=1..n} 1/(prime(k) - 1)^2.

%C Lim_{n -> infinity} A119686(n)/a(n) = A086242.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimeSums.html">Prime Sums</a>.

%e The first few fractions are 1, 5/4, 21/16, 193/144, 4861/3600, 2443/1800, 78401/57600, 707209/518400, ... = A119686/A334746.

%t Denominator @ Accumulate @ Table[1/(Prime[k] - 1)^2, {k, 1, 21}] (* _Amiram Eldar_, May 12 2020 *)

%o (PARI) a(n) = denominator(sum(k=1, n, 1/(prime(k) - 1)^2)); \\ _Michel Marcus_, May 12 2020

%Y Cf. A000040, A006093, A086242, A119686 (numerators).

%K nonn,frac

%O 1,2

%A _Petros Hadjicostas_, May 11 2020

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Last modified May 18 22:36 EDT 2021. Contains 344005 sequences. (Running on oeis4.)