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%I #29 Feb 09 2024 03:26:19
%S 4,4,0,6,8,6,7,9,3,5,0,9,7,7,1,5,1,2,6,1,6,3,0,4,6,6,2,4,8,9,8,9,6,1,
%T 5,4,5,1,4,0,8,0,1,6,4,1,3,0,8,1,7,7,0,5,3,7,6,6,4,7,8,0,4,3,2,6,6,8,
%U 8,5,9,2,1,1,1,0,1,3,0,4,3,9,1,6,8,5,3,4,4,5,9,5,5,1,2,8,0,2,1,4,2,8
%N Decimal expansion of the Ising constant K_c, the ratio of the coupling constant to the ferromagnetic critical temperature, in the two-dimensional case.
%D Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.22 Lenz-Ising Constants, p. 396.
%H Andrei Okounkov, <a href="https://doi.org/10.1090/bull/1512">Limit shapes, real and imagined</a>, Bull. Amer. Math. Soc. 53 2 (2016), 187-216
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Ising_model">Ising Model</a>.
%F K_c = (1/2)*log(1 + sqrt(2)) = (1/2)*A091648.
%F Equals Integral_{0..1} x/sqrt(1 + x^4) dx. - _Peter Bala_, Oct 28 2019
%F Equals arcsinh(1)/2. - _Peter Luschny_, Oct 29 2019
%F Equals arctanh(sqrt(2)-1). - _Amiram Eldar_, Feb 09 2024
%e 0.4406867935097715126163046624898961545140801641308177053766478...
%t RealDigits[(1/2)*Log[1 + Sqrt[2]], 10, 102] // First
%Y Cf. A091648.
%K nonn,cons,easy
%O 0,1
%A _Jean-François Alcover_, Jul 30 2014
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