OFFSET
1,4
COMMENTS
LINKS
Alois P. Heinz, Rows n = 1..13, flattened
Wikipedia, Chromatic Polynomial
Wikipedia, Triangular grid graph
EXAMPLE
4 example graphs: o
/ \
o o---o
/ \ / \ / \
o o---o o---o---o
/ \ / \ / \ / \ / \ / \
o o---o o---o---o o---o---o---o
n: 1 2 3 4
Vertices: 1 3 6 10
Edges: 0 3 9 18
The 2 X 2 X 2 triangular grid is equal to the cycle graph C_3 with chromatic polynomial q^3 -3*q^2 +2*q => [1, -3, 2, 0].
Triangle T(n,k) begins:
1, 0;
1, -3, 2, 0;
1, -9, 32, -56, 48, -16, 0;
1, -18, 144, -672, 2016, -4031, 5368, ...
1, -30, 419, -3612, 21477, -93207, 304555, ...
1, -45, 965, -13115, 126720, -925528, 5303300, ...
...
CROSSREFS
KEYWORD
AUTHOR
Alois P. Heinz, Jul 20 2011
STATUS
approved