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A068271
1/4 the number of colorings of an n X n rhombic hexagonal array with 4 colors.
4
1, 12, 264, 11424, 1008576, 184910592, 71033971200, 57469424744448, 98237339264864256, 355574469749489123328, 2729407814499050197254144, 44482040254775494064841818112, 1540473331004371306422199656382464, 113440401780206156918876627438624833536
OFFSET
1,2
COMMENTS
Terms for rhombic- and staggered- hexagonal arrays are the same for n in 1..4.
LINKS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 24 2002
EXTENSIONS
a(9) from Alois P. Heinz, May 02 2012
a(10)-a(14) from Andrew Howroyd, Jun 25 2017
STATUS
approved