306488domain: NAppears in sequencesFibonacci sequence beginning 0, 28.at n=21A022362Number of planar n X n X n binary triangular grids symmetric both under 120 degree rotation and reflection with no more than 2 ones in any 2 X 2 X 2 subtriangle.at n=15A153910G.f. is the fourth power of the g.f. of A006950.at n=20A273228