A002707 - OEIS

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A002707

Number of ternary trees with n nodes.
(Formerly M3128 N1268)

1, 1, 3, 31, 8401, 100130704103, 167321084032306100365838018661441, 780729803567659232170209385771412393899822868427528396719062233553621064241305757906662806984051 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	REFERENCES	`Z. A. Melzak, A note on homogeneous dendrites, Canad. Math. Bull., 11 (1968), 85-93.` `N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).` `N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).`
	LINKS	`Index entries for sequences related to trees`
	FORMULA	`a(n) = a(n-1)(a(n-1)+a(n-2))(a(n-1)+a(n-2)+a(n-3))/6 + a(n-1)(a(n-1)+a(n-2))/(a(n-2)+a(n-3))(a(n-1)/a(n-2)-a(n-2)/a(n-3)) + a(n-1)^2/a(n-2).`
	CROSSREFS	`Sequence in context: A022499 A129209 A134721 * A144964 A168678 A118913` `Adjacent sequences: A002704 A002705 A002706 * A002708 A002709 A002710`
	KEYWORD	`nonn,nice,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`
	EXTENSIONS	`More terms and recurrence from James A. Sellers (sellersj(AT)math.psu.edu), Feb 14 2000`

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Last modified February 16 17:11 EST 2012. Contains 205938 sequences.