login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A274081 Number of unrooted labeled trees on 3n+2 nodes with node degree either one or four. 2
1, 5, 560, 277200, 369969600, 1040623584000, 5318844410880000, 44743448895425280000, 577102758498249984000000, 10821132329283106871040000000, 283002122589833107696435200000000, 9986037506585076241055342592000000000, 462684151212030123561950840428953600000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

There are no unrooted labeled trees on 3n or 3n+1 nodes with node degree either one or four.

LINKS

Table of n, a(n) for n=0..12.

Math.Stackexchange.com, Marko Riedel et al., Number of labeled trees

MAPLE

seq(binomial(3*n+2, n)*(3*n)!/(3!^n), n=0..16);

MATHEMATICA

Table[Binomial[3*n+2, n]*(3*n)!/(3!)^n, {n, 0, 10}] (* G. C. Greubel, Jun 09 2016 *)

CROSSREFS

Cf. A274056, A000272.

Sequence in context: A112900 A259463 A241802 * A153404 A297821 A297991

Adjacent sequences:  A274078 A274079 A274080 * A274082 A274083 A274084

KEYWORD

nonn

AUTHOR

Marko Riedel, Jun 09 2016

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 6 01:03 EDT 2021. Contains 343579 sequences. (Running on oeis4.)