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%I #14 Dec 20 2022 01:47:01
%S 6,7,6,5,6,5,1,3,6,1,4,7,9,6,6,6,4,0,8,2,6,4,7,2,0,1,6,2,4,6,1,2,9,8,
%T 1,3,4,5,4,3,9,5,2,1,2,1,8,5,9,5,5,6,3,2,3,0,6,0,0,8,6,1,3,1,6,5,4,6,
%U 8,5,0,8,2,4,3,6,7,5,9,2,1,1,1,9,8,2,1
%N Decimal expansion of Sum_{k>=2} (1/k)*arctanh(1/k).
%H Michael Ian Shamos, <a href="https://citeseerx.ist.psu.edu/doc_view/pid/ae33a269baba5e8b1038e719fb3209e8a00abec5">Shamos's Catalog of the Real Numbers</a>, 2011, p. 564.
%F Equals Sum_{k>=2} arccoth(k)/k.
%F Equals Sum_{k>=1} (zeta(2*k)-1)/(2*k-1).
%F Equals log(Product_{k>=2} ((k+1)/(k-1))^(1/(2*k))).
%e 0.67656513614796664082647201...
%t RealDigits[N[Sum[ArcTanh[1/k]/k, {k, 2, Infinity}], 30], 10, 26][[1]] (* _Amiram Eldar_, Jul 21 2022 *)
%Y Cf. A016655, A355921, A355923.
%K nonn,cons
%O 0,1
%A _Amiram Eldar_, Jul 21 2022
%E More terms from _Jinyuan Wang_, Jul 21 2022
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