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 A220821 Number of rooted binary leaf-multilabeled trees with n leaves on the label set [4]. 2

%I

%S 0,0,0,15,240,2604,24180,207732,1710108,13739550,108853512,855732465,

%T 6700902804,52395480996,409733313444,3207687963129,25155951725808,

%U 197703130100532,1557413160706764,12298597436673711,97359729090421320,772615510913274126,6145842794363133324

%N Number of rooted binary leaf-multilabeled trees with n leaves on the label set [4].

%H Andrew Howroyd, <a href="/A220821/b220821.txt">Table of n, a(n) for n = 1..200</a>

%H V. P. Johnson, <a href="http://people.math.sc.edu/czabarka/Theses/JohnsonThesis.pdf">Enumeration Results on Leaf Labeled Trees</a>, Ph. D. Dissertation, Univ. Southern Calif., 2012.

%p b:= proc(n, k) option remember; `if`(n<2, k*n, `if`(n::odd, 0,

%p (t-> t*(1-t)/2)(b(n/2, k)))+add(b(i, k)*b(n-i, k), i=1..n/2))

%p end:

%p a:= n-> (k-> add((-1)^i*binomial(k, i)*b(n, k-i), i=0..k))(4):

%p seq(a(n), n=1..30); # _Alois P. Heinz_, Sep 07 2019

%t A[n_, k_] := A[n, k] = If[n < 2, k n, If[OddQ[n], 0, (# (1 - #)/2)&[A[n/2, k]]] + Sum[A[i, k] A[n - i, k], {i, 1, n/2}]];

%t T[n_, k_] := Sum[(-1)^i Binomial[k, i] A[n, k - i], {i, 0, k}];

%t a[n_] := T[n, 4];

%t Array[a, 23] (* _Jean-François Alcover_, Sep 02 2019, after _Alois P. Heinz_ in A319541 *)

%Y Column k=4 of A319541.

%K nonn

%O 1,4

%A _N. J. A. Sloane_, Dec 22 2012

%E Terms a(11) and beyond from _Andrew Howroyd_, Sep 23 2018

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Last modified December 12 09:36 EST 2019. Contains 329953 sequences. (Running on oeis4.)