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A330966 a(n) is 1/5 times the number of anti-chains of size four in "0,1,2" Motzkin trees on n edges. 0
1, 11, 84, 520, 2835, 14133, 65960, 292536, 1245789, 5132375, 20569512, 80541300, 309143065, 1166302239, 4334300976, 15895046840, 57608669274, 206606077758, 733992204988, 2585415612500, 9036556157100, 31362262768684, 108144498780096, 370700681812032 (list; graph; refs; listen; history; text; internal format)
OFFSET

6,2

COMMENTS

See A335355 for details.

LINKS

Table of n, a(n) for n=6..29.

Lifoma Salaam, Combinatorial statistics on phylogenetic trees, Ph.D. Dissertation, Howard University, Washington D.C., 2008; see Definition 42 (p. 30), Theorem 44 (p. 33), and Table 2.4 (p. 39).

FORMULA

a(n) = A335355(n)/5.

PROG

(PARI) default(seriesprecision, 50);

M(z) = (1 - z - sqrt(1 - 2*z - 3*z^2))/(2*z^2); /* g.f. of A001006 */

T(z) = 1/sqrt(1 - 2*z - 3*z^2); /* g.f. of A002426 */

for(n=0, 30, print1(polcoef(z^6*T(z)^7*M(z)^4, n, z), ", "))

CROSSREFS

Cf. A001006, A002426, A335355.

Sequence in context: A191003 A012478 A239461 * A026783 A244975 A271558

Adjacent sequences:  A330963 A330964 A330965 * A330967 A330968 A330969

KEYWORD

nonn

AUTHOR

Petros Hadjicostas, Jun 08 2020

STATUS

approved

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Last modified July 24 14:51 EDT 2021. Contains 346273 sequences. (Running on oeis4.)