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%I #10 May 05 2022 07:28:05
%S 1,3,45,315,1575,51975,4729725,4729725,18555075,4583103525,
%T 50414138775,1159525191825,793359341775,15073827493725,
%U 2185704986590125,67756854584293875,1151866527932995875,3455599583798987625,2429286507410688300375,2429286507410688300375
%N Denominator of b(n) = Sum_{k=1..n} (-1)^(k+1)/k*Sum_{i=0..k-1} (-1)^i/(2*i+1).
%H Amiram Eldar, <a href="/A073595/b073595.txt">Table of n, a(n) for n = 1..772</a>
%F Limit_{n -> infinity} b(n) = G, the Catalan constant (A006752).
%t Denominator[Accumulate[Table[(-1)^(k + 1)/k * Sum[(-1)^i/(2*i + 1), {i, 0, k - 1}], {k, 1, 20}]]] (* _Amiram Eldar_, May 05 2022 *)
%o (PARI) a(n)=denominator(sum(k=1,n,(-1)^(k+1)/k*sum(i=0,k-1,(-1)^i/(2*i+1))))
%Y Cf. A006752, A073594 (numerators).
%K easy,frac,nonn
%O 1,2
%A _Benoit Cloitre_, Aug 28 2002
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