A245725 Decimal expansion of z_tri, a constant related to the enumeration of spanning trees on the triangular lattice (this is different from A242968).
1, 6, 1, 5, 3, 2, 9, 7, 3, 6, 0, 9, 7, 2, 5, 2, 5, 7, 0, 4, 6, 8, 1, 8, 2, 5, 5, 3, 6, 1, 9, 0, 3, 1, 9, 7, 0, 3, 6, 1, 2, 0, 9, 2, 0, 3, 9, 0, 2, 9, 3, 5, 0, 8, 0, 6, 5, 4, 3, 4, 2, 3, 5, 1, 8, 0, 5, 0, 7, 5, 5, 6, 4, 0, 3, 6, 3, 4, 9, 2, 1, 0, 4, 1, 8, 9, 3, 8, 0, 4, 5, 4, 4, 6, 8, 5, 6, 9, 6, 0, 3, 6, 7, 4
Offset: 1
Examples
1.6153297360972525704681825536190319703612092039029350806543423518...
References
- Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.22 Lenz-Ising Constants, p. 400.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
- Robert Shrock and F. Y. Wu, Spanning Trees on Graphs and Lattices in d Dimensions, arXiv:cond-mat/0004341 [cond-mat.stat-mech], 2000, p. 7.
Programs
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Mathematica
H = Sqrt[3]/(6*Pi)*PolyGamma[1, 1/6] - Pi/Sqrt[3] - Log[6]; RealDigits[Log[2] + Log[3] + H, 10, 104] // First (* or *) 3*(Sqrt[3]/Pi)*N[Sum[1/n^2 - 1/(n+4)^2, {n, 1, Infinity, 6}], 104] // RealDigits // First
Formula
Equals log(2) + log(3) + H, where H is the auxiliary constant A242967.
Equals Sum_{n>=1} 10*n*(arccoth((3*n) / 2) - 2 * arccoth(3*n)). - Antonio Graciá Llorente, Oct 13 2024