A004113 Number of rooted trees with n nodes and 2-colored non-leaf nodes. (Formerly M1629)

1, 2, 6, 18, 60, 204, 734, 2694, 10162, 38982, 151920, 599244, 2389028, 9608668, 38945230, 158904230, 652178206, 2690598570, 11151718166, 46412717826, 193891596436, 812748036380, 3417407089470, 14410094628558, 60920843101858, 258169745573158, 1096494947168142

Offset

1,2

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Alois P. Heinz, Table of n, a(n) for n = 1..500

F. Harary, R. W. Robinson and A. J. Schwenk, Twenty-step algorithm for determining the asymptotic number of trees of various species, J. Austral. Math. Soc., Series A, 20 (1975), 483-503. Errata: Vol. A 41 (1986), p. 325.

N. J. A. Sloane, Transforms

Index entries for sequences related to rooted trees

Index entries for sequences related to trees

Formula

Shifts left and halves under EULER transform.

a(n) ~ c * d^n / n^(3/2), where d = 4.49415643203339504537343052838796824... and c = 0.368722987377516657464802259... - Vaclav Kotesovec, Feb 28 2014

Maple

with(numtheory): etr:= proc(p) local b; b:= proc(n) option remember; `if`(n=0, 1, (add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n))/n) end end: b:= etr(a): a:= n-> `if`(n<=1, n, 2*b(n-1)): seq(a(n), n=1..30); # Alois P. Heinz, Sep 06 2008

Mathematica

etr[p_] := Module[{b}, b[n_] := b[n] = If[n == 0, 1, Sum[Sum[d*p[d], {d, Divisors[j]}]*b[n - j], {j, 1, n}]/n ]; b]; b = etr[a]; a[n_] := If[n <= 1, n, 2*b[n - 1]]; Table[a[n], {n, 1, 27}] (* Jean-François Alcover, Jan 29 2013, translated from Alois P. Heinz's Maple program *)

Crossrefs

Cf. A004114, A052316, A052317.

Sequence in context: A150043 A048117 A048118 * A150044 A108531 A150045

Adjacent sequences: A004110 A004111 A004112 * A004114 A004115 A004116

Keyword

nonn,eigen

Author

N. J. A. Sloane

Extensions

Extended with better description from Christian G. Bower, Apr 15 1998

Status

approved