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A005173 Number of trees of subsets of an n-set.
(Formerly M4844)
1
0, 1, 12, 61, 240, 841, 2772, 8821, 27480, 84481, 257532, 780781, 2358720, 7108921, 21392292, 64307941, 193185960, 580082161, 1741295052, 5225982301, 15682141200, 47054812201, 141181213812, 423577195861, 1270798696440 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

F. R. McMorris and T. Zaslavsky, The number of cladistic characters, Math. Biosciences, 54 (1981), 3-10.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..25.

F. R. McMorris and T. Zaslavsky, The number of cladistic characters, Math. Biosciences, 54 (1981), 3-10. [Annotated scanned copy]

Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992.

Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992.

Index entries for sequences related to trees

FORMULA

G.f.: x ( 1 + 6 x ) / ( 1 - x ) ( 1 - 2 x ) ( 1 - 3 x ).

First differences give A003063, 3^(n-1)-2^n.

MAPLE

A005173:=-z*(1+6*z)/(z-1)/(3*z-1)/(2*z-1); [Conjectured by Simon Plouffe in his 1992 dissertation.]

CROSSREFS

Sequence in context: A240002 A114241 A127766 * A196144 A294682 A177677

Adjacent sequences:  A005170 A005171 A005172 * A005174 A005175 A005176

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Larry Reeves (larryr(AT)acm.org), Feb 06 2001

STATUS

approved

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Last modified November 14 17:16 EST 2019. Contains 329126 sequences. (Running on oeis4.)