644436domain: NAppears in sequencesNumber of planar n X n X n binary triangular grids symmetric both under 120-degree rotation and reflection with no more than 1 one in any 2 X 2 X 2 subtriangle.at n=19A153898Expansion of (-1 + Product_{k>=1} 1 / (1 - x^k))^3.at n=19A341221