login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A036506 Number of labeled 4-trees with n nodes. 8
0, 0, 0, 1, 1, 15, 455, 20230, 1166886, 82031250, 6768679170, 639276644655, 67876292150095, 7992910154350121, 1032869077119140625, 145221924661653841820, 22060305511905816000860, 3599313659344525384083060, 627583654087024080928783956 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

REFERENCES

F. Harary and E. Palmer, Graphical Enumeration, (1973), p. 30, Problem 1.13(b) with k=4.

LINKS

T. D. Noe, Table of n, a(n) for n=1..100

Index entries for sequences related to trees

FORMULA

a(n) = C(n,4)*(4*n-15)^(n-6).

Number of labeled k-trees on n nodes is binomial(n, k) * (k(n-k)+1)^(n-k-2).

CROSSREFS

Cf. A000272 (labeled trees), A036361 (labeled 2-trees), A036362 (labeled 3-trees), A036506 (labeled 4-trees), A000055 (unlabeled trees), A054581 (unlabeled 2-trees).

Sequence in context: A020285 A041423 A041420 * A219561 A209488 A320097

Adjacent sequences:  A036503 A036504 A036505 * A036507 A036508 A036509

KEYWORD

nonn,changed

AUTHOR

N. J. A. Sloane.

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 23 15:28 EDT 2018. Contains 316528 sequences. (Running on oeis4.)