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A182798 Number of 4-colorings of the Triangle Graph of order n. 12
4, 24, 192, 2112, 32640, 718080, 22665216, 1031276544, 67849629696, 6468240187392, 894839431299072, 179851071814434816, 52561241074964496384, 22351071118387029737472, 13837189739906569661841408 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The Triangle Graph of order n has n rows with k vertices in row k. Each vertex is connected to the neighbors in the same row and up to two vertices in each of the neighboring rows. The Graph has A000217(n) vertices and 3*A000217(n-1) edges altogether.

LINKS

Table of n, a(n) for n=1..15.

Eric Weisstein's World of Mathematics, Triangle Graph

Wikipedia, Chromatic polynomial

FORMULA

a(n) = 4 * A153467(n).

CROSSREFS

4th row of A182797. Cf. A178435, A182788, A182789, A182790, A182791, A182792, A182793, A182794, A182795, A182796.

Sequence in context: A349514 A293021 A002866 * A073840 A024249 A007145

Adjacent sequences:  A182795 A182796 A182797 * A182799 A182800 A182801

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Dec 02 2010

EXTENSIONS

a(15) from Alois P. Heinz, Mar 11 2016

STATUS

approved

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Last modified December 1 16:44 EST 2021. Contains 349430 sequences. (Running on oeis4.)