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A058521 B-trees of order 5 with n labeled leaves. 2
1, 1, 1, 2, 3, 4, 7, 11, 20, 36, 67, 121, 215, 377, 657, 1154, 2045, 3666, 6628, 12063, 22079, 40642, 75264, 140191, 262457, 493297, 929703, 1754941, 3314509, 6258052, 11803995, 22232306, 41801393, 78453563, 146987053, 274957984 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..36.

Index entries for sequences related to rooted trees

FORMULA

G.f. A(x) satisfies: A(x) = x + A(x^2+x^3+x^4+x^5). [Geoffrey Critzer, Mar 28 2013]

MAPLE

spec := [ B, {B=Union(Z, Subst(M, B)), M=Union(Prod(Z, Z), Prod(Z, Z, Z), Prod(Z$4), Prod(Z$5))} ]: [seq(combstruct[count](spec, size=n), n=1..40)];

MATHEMATICA

nn=38; f[x_]:=Sum[a[n]x^n, {n, 0, nn}]; a[0]=0; sol=SolveAlways[0==Series[f[x]-x-f[x^2+x^3+x^4+x^5], {x, 0, nn}], x]; Table[a[n], {n, 0, nn}]/.sol  (* Geoffrey Critzer, Mar 28 2013 *)

CROSSREFS

Cf. A014535, A037026.

Sequence in context: A188624 A256994 A107481 * A116628 A140463 A223578

Adjacent sequences:  A058518 A058519 A058520 * A058522 A058523 A058524

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 21 2000

STATUS

approved

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Last modified June 15 20:50 EDT 2019. Contains 324145 sequences. (Running on oeis4.)