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A245592
Decimal expansion of the Ising constant K_c, the ratio of the coupling constant to the ferromagnetic critical temperature, in the two-dimensional case.
1
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, 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, 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
OFFSET
0,1
REFERENCES
Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.22 Lenz-Ising Constants, p. 396.
LINKS
Andrei Okounkov, Limit shapes, real and imagined, Bull. Amer. Math. Soc. 53 2 (2016), 187-216
Wikipedia, Ising Model.
FORMULA
K_c = (1/2)*log(1 + sqrt(2)) = (1/2)*A091648.
Equals Integral_{0..1} x/sqrt(1 + x^4) dx. - Peter Bala, Oct 28 2019
Equals arcsinh(1)/2. - Peter Luschny, Oct 29 2019
Equals arctanh(sqrt(2)-1). - Amiram Eldar, Feb 09 2024
EXAMPLE
0.4406867935097715126163046624898961545140801641308177053766478...
MATHEMATICA
RealDigits[(1/2)*Log[1 + Sqrt[2]], 10, 102] // First
CROSSREFS
Cf. A091648.
Sequence in context: A155502 A228048 A016705 * A169783 A133657 A121455
KEYWORD
nonn,cons,easy
AUTHOR
STATUS
approved