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 A130034 Denominators of partial sums of a series for the inverse of the arithmetic-geometric mean (agM) of 1 and sqrt(2)/2. 3

%I

%S 1,8,256,2048,262144,2097152,67108864,536870912,274877906944,

%T 2199023255552,70368744177664,562949953421312,72057594037927936,

%U 576460752303423488,18446744073709551616,147573952589676412928

%N Denominators of partial sums of a series for the inverse of the arithmetic-geometric mean (agM) of 1 and sqrt(2)/2.

%C See the references and the W. Lang link under A129934.

%H G. C. Greubel, <a href="/A130034/b130034.txt">Table of n, a(n) for n = 0..665</a>

%F a(n) = denom(sum((((2*j)!/(j!^2))^2)*(1/2^(5*j)),j=0..n)), n>=0.

%t Denominator[Table[Sum[(((2*k)!/(k!^2))^2)*(1/2^(5*k)), {k,0,n}], {n,0, 50}]] (* _G. C. Greubel_, Aug 17 2018 *)

%o (PARI) for(n=0,50, print1(denominator(sum(k=0,n, (((2*k)!/(k!^2))^2)*(1/2^(5*k)))), ", ")) \\ _G. C. Greubel_, Aug 17 2018

%K nonn,frac,easy

%O 0,2

%A _Wolfdieter Lang_ Jun 01 2007

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Last modified August 4 09:41 EDT 2021. Contains 346446 sequences. (Running on oeis4.)