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Number of planar n X n X n binary triangular grids symmetric under 120 degree rotation with every one adjacent to exactly 2 other ones.
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%I #3 Mar 31 2012 12:35:21

%S 1,1,2,2,2,4,9,15,37,88,191,729,2246,6555,31434,144150,601688,3970089,

%T 24322158,135488789,1251604698,10410417129,79632436378,997602199170,

%U 11483571472544,120898733308159,2073714604283068,32605974669636948

%N Number of planar n X n X n binary triangular grids symmetric under 120 degree rotation with every one adjacent to exactly 2 other ones.

%K nonn

%O 0,3

%A _R. H. Hardin_ Jan 04 2009