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A245725
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Decimal expansion of z_tri, a constant related to the enumeration of spanning trees on the triangular lattice (this is different from A242968).
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6
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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
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OFFSET
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1,2
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REFERENCES
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Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.22 Lenz-Ising Constants, p. 400.
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LINKS
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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 p. 7.
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FORMULA
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log(2) + log(3) + H, where H is the auxiliary constant A242967.
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EXAMPLE
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1.6153297360972525704681825536190319703612092039029350806543423518...
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MATHEMATICA
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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
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CROSSREFS
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Cf. A242967, A242968, A242969.
Sequence in context: A010137 A245967 A212006 * A011096 A347177 A195695
Adjacent sequences: A245722 A245723 A245724 * A245726 A245727 A245728
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KEYWORD
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nonn,cons,easy
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AUTHOR
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Jean-François Alcover, Jul 30 2014
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STATUS
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approved
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