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A220817 Number of rooted binary MUL-trees with n leaves on the label set [4]. 2
4, 10, 40, 215, 1260, 8010, 53240, 366680, 2590420, 18674660, 136809240, 1015603015, 7622900360, 57753364510, 441081947840, 3392237023425, 26248421645200, 204202630151860, 1596256637347240, 12531697773337965, 98763817012822460, 781102051887068160 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..200

V. P. Johnson, Enumeration Results on Leaf Labeled Trees, Ph. D. Dissertation, Univ. Southern Calif., 2012.

MATHEMATICA

a[n_] := a[n] = If[n < 2, 4 n, If[OddQ[n], 0, (# (1 - #)/2 &)[a[n/2]]] + Sum[a[i] a[n - i], {i, 1, n/2}]];

Array[a, 25] (* Jean-Fran├žois Alcover, Sep 02 2019, after Alois P. Heinz in A319539 *)

CROSSREFS

Column k=4 of A319539.

Sequence in context: A263551 A007173 A222367 * A114918 A224488 A149213

Adjacent sequences:  A220814 A220815 A220816 * A220818 A220819 A220820

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 22 2012

EXTENSIONS

Terms a(11) and beyond from Andrew Howroyd, Sep 23 2018

STATUS

approved

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Last modified November 22 18:55 EST 2019. Contains 329410 sequences. (Running on oeis4.)