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A166736
Consider triangles stacked so the k-th row has 2*k-1 triangles. a(n) is the number of ways to color each triangle in the first n rows using three colors with the restriction that adjacent triangles must be different colors. (Triangles are adjacent if they share a side.)
0
3, 24, 528, 31968, 5332224, 2450774016, 3104112826368
OFFSET
1,1
EXAMPLE
Illustration of first two rows:
/\
/ \
/ 1 \
/ \
/________\
/\ /\
/ \ / \
/ 2 \ 3 / 4 \
/ \ / \
/________\/________\
Triangles sharing a side are considered adjacent; e.g., 1 & 3 are adjacent in the figure, 1 & 2 are not.
CROSSREFS
Sequence in context: A279165 A336577 A194157 * A330297 A109055 A318766
KEYWORD
nonn
AUTHOR
Chris Cole (chris(AT)questrel.com), Oct 20 2009
EXTENSIONS
Edited by Jon E. Schoenfield, Jul 08 2017
Name simplified by Charles R Greathouse IV, Jul 09 2017
STATUS
approved