The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A003092 Number of labeled plane 2-trees with n nodes. (Formerly M2159) 2
 0, 1, 2, 36, 1200, 57000, 3477600, 257826240, 22438563840, 2238543216000, 251584613280000, 31431367287936000, 4319334744012288000, 647313578549730892800, 105041172967733882880000, 18345770194541665075200000, 3430869798262479024291840000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 REFERENCES F. Harary and E. Palmer, Graphical Enumeration, (1973), p. 30, Problem 1.14. E. M. Palmer and R. C. Read, on the number of plane 2-trees, J. Lond. Math. Soc., 6 (1973), 583-592. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS E. M. Palmer and R. C. Read, On the number of plane 2-trees, J. Lond. Math. Soc., 6 (1973), 583-592. [Annotated and corrected scanned copy] FORMULA n(n-1)^2 (5n-10)!/(4n-6)!. MAPLE [ seq(n*(n-1)^2*(5*n-10)!/(4*n-6)!, n=2..20) ]; CROSSREFS Sequence in context: A210899 A302903 A259467 * A187535 A263421 A046673 Adjacent sequences:  A003089 A003090 A003091 * A003093 A003094 A003095 KEYWORD nonn AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 26 14:20 EST 2022. Contains 350598 sequences. (Running on oeis4.)