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A212809 Decimal expansion of radius of convergence of g.f. for unlabeled trees (A000055). 1
3, 3, 8, 3, 2, 1, 8, 5, 6, 8, 9, 9, 2, 0, 7, 6, 9, 5, 1, 9, 6, 1, 1, 2, 6, 2, 5, 7, 1, 7, 0, 1, 7, 0, 5, 3, 1, 8, 3, 7, 7, 4, 6, 0, 7, 5, 3, 2, 9, 6, 7, 7, 9, 5, 5, 7, 2, 3, 0, 3, 7, 7, 6, 2, 5, 7, 6, 6, 6, 0, 5, 0, 1, 8, 9, 6, 2, 0, 7, 6, 6, 5, 6, 3, 5, 2, 8, 7, 9, 8, 3, 6, 7, 3 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..93.

M. Drmota, B. Gittenberger, The shape of unlabeled rooted random trees, Eur. J. Comb. 31 (2010) no 8, 2028-2063

E. M. Palmer and A. J. Schwenk, On the number of trees in a random forest, J. Combin. Theory, B 27 (1979), 109-121.

FORMULA

Equals 1/A051491. - Vaclav Kotesovec, Jul 29 2013

EXAMPLE

0.338321856899208...

MATHEMATICA

digits = 95; max = 200;

s[n_, k_] := s[n, k] = a[n + 1 - k] + If[n < 2*k, 0, s[n - k, k]];

a[1] = 1;

a[n_] := a[n] = Sum[a[k]*s[n - 1, k]*k, {k, 1, n - 1}]/(n - 1);

A[x_] := Sum[a[k]*x^k, {k, 0, max}];

eq = Log[c] == 1 + Sum[A[c^-k]/k, {k, 2, max}];

r = 1/c /. FindRoot[eq, {c, 3}, WorkingPrecision -> digits + 5];

RealDigits[r, 10, digits] // First (* Jean-Fran├žois Alcover, Aug 10 2016 *)

CROSSREFS

Cf. A000055.

Sequence in context: A164040 A154178 A276800 * A294643 A029614 A143615

Adjacent sequences:  A212806 A212807 A212808 * A212810 A212811 A212812

KEYWORD

nonn,cons

AUTHOR

N. J. A. Sloane, May 29 2012

EXTENSIONS

More terms from Vaclav Kotesovec, Jul 29 2013

STATUS

approved

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Last modified October 23 12:00 EDT 2018. Contains 316527 sequences. (Running on oeis4.)