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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A063689 Number of 2-trees rooted at a triangle with 3 similar edges. 0
1, 1, 2, 6, 21, 83, 356, 1599, 7434, 35381, 171508, 843419, 4197179, 21094355 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 76, Eq. (3.5.17).

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

Sequence really begins 1, 0, 0, 1, 0, 0, 2, 0, 0, 6, 0, 0, 21, 0, 0, 83, 0, 0, 356, ... but only nonzero trisection is shown.

CROSSREFS

Cf. A005750, A058870, A058866, A054581.

Sequence in context: A032346 A148495 A150221 * A058866 A178325 A087649

Adjacent sequences:  A063686 A063687 A063688 * A063690 A063691 A063692

KEYWORD

more,nonn

AUTHOR

Vladeta Jovovic, Aug 22 2001

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 November 21 11:01 EST 2018. Contains 317447 sequences. (Running on oeis4.)