OFFSET
1,8
COMMENTS
The entries in the triangle have been obtained - painstakingly - from the Read & Wilson reference (pp. 63-73); the white vertices indicate the possible distinct rootings for the given tree.
REFERENCES
R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
LINKS
Sean A. Irvine, Rows n=1..44 of triangle, flattened
F. Harary, R. W. Robinson, Isomorphic factorizations VIII: bisectable trees, Combinatorica 4 (2) (1984) 169-179.
FORMULA
EXAMPLE
Row 4 is 0,2,0,0 because the trees with 4 vertices are (i) the path tree abcd with 2 distinct rootings (at a and at b) and (ii) the star tree with 4 vertices having, obviously, 2 distinct rootings.
Triangle starts:
1;
1, 0;
0, 1, 0;
0, 2, 0, 0;
0, 1, 1, 1, 0;
0, 2, 1, 2, 1, 0;
0, 1, 2, 4, 1, 2, 1;
CROSSREFS
AUTHOR
Emeric Deutsch, Oct 20 2013
STATUS
approved