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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 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.)