|
|
A056814
|
|
Triangle partitions of order n: topologically distinct ways to dissect a triangle into n triangles.
|
|
2
|
|
|
|
OFFSET
|
2,2
|
|
LINKS
|
Z. Skupien, A. Zak, Pair-sums packing and rainbow cliques, in Topics In Graph Theory, A tribute to A. A. and T. E. Zykovs on the occasion of A. A. Zykov's 90th birthday, ed. R. Tyshkevich, Univ. Illinois, 2013, pages 131-144, (in English and Russian).
|
|
EXAMPLE
|
a(2) = 1 because up to equivalence, there is only one partition of a triangle in two smaller ones, using a segment from one vertex to a point on the opposite side. (Here and below, "on" excludes the endpoints.)
a(3) = 4 is the number of partitions of a triangle ABC into three smaller ones: One uses three segments AD, BD and CD, where D is a point inside ABC. Three other topologically inequivalent partitions of order 3 each use two segments, as follows: {AE, AF}, {AE, EG} and {AE, BH}, where E and F are two distinct points on BC, G is a point on AB, and H is a point on AE. (End)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,nice,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|