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A245655
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Decimal expansion of eta_A, a constant associated with the asymptotics of the enumeration of labeled acyclic digraphs.
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0
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5, 7, 4, 3, 6, 2, 3, 7, 3, 3, 0, 9, 3, 1, 1, 4, 7, 6, 9, 1, 6, 6, 7, 0, 8, 0, 1, 6, 8, 1, 5, 0, 7, 2, 4, 6, 9, 7, 2, 1, 8, 8, 4, 6, 0, 9, 7, 0, 8, 7, 5, 4, 2, 4, 0, 6, 9, 0, 2, 2, 4, 7, 9, 1, 2, 2, 0, 2, 8, 6, 8, 9, 4, 0, 3, 7, 1, 7, 7, 3, 3, 7, 7, 1, 5, 7, 3, 8, 0, 5, 2, 5, 3, 5, 4, 1, 0, 6, 4, 2, 6, 9, 4
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OFFSET
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0,1
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COMMENTS
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The article "Acyclic digraphs and eigenvalues of (0,1)-matrices" gives the wrong value M=0.474! See A003024 for more. - Vaclav Kotesovec, Jul 28 2014
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REFERENCES
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Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.6 Otter's Tree Enumeration Constants, p. 310.
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LINKS
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FORMULA
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eta_A = xi_A*lambda(xi_A/2), where xi_A is the smallest positive root of lambda(x) = sum_{n >= 0} (-1)^n*x^n/(2^(n*(n-1)/2)*n!).
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EXAMPLE
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0.5743623733093114769166708016815072469721884609708754240690224791220286894...
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MATHEMATICA
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digits = 103; lambda[x_?NumericQ] := NSum[(-1)^n*x^n/(2^(n*(n - 1)/2)*n!), {n, 0, Infinity}, WorkingPrecision -> digits + 10, Method -> "AlternatingSigns"]; xi = x /. FindRoot[lambda[x] == 0, {x, 3/2}, WorkingPrecision -> digits + 10]; RealDigits[xi*lambda[xi/2], 10, digits] // First
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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