A063688 Number of 2-trees rooted at a triangle.

1, 1, 3, 10, 39, 164, 746, 3474, 16658, 81166, 401169, 2004517, 10110757, 51402250, 263133142, 1355126922, 7016115632, 36498130908, 190673015083, 999932115039, 5262094054524, 27779114013628, 147072756065567, 780722981065006

Offset

1,3

References

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 76, Eq. (3.5.13).

Links

Table of n, a(n) for n=1..24.

Crossrefs

Cf. A005750, A058870, A058866, A054581.

Sequence in context: A151072 A151073 A363555 * A245378 A350915 A221585

Adjacent sequences: A063685 A063686 A063687 * A063689 A063690 A063691

Keyword

nonn

Author

Vladeta Jovovic, Aug 22 2001

Status

approved