190622domain: NAppears in sequencesNumber of planar n X n X n binary triangular grids with mirror symmetry about one altitude with no more than 1 one in any 5 X 5 X 5 subtriangle.at n=20A153906G.f. A(x) satisfies: 1-x = Sum_{n>=0} (A(x)^n + x^n)^n * (-x)^n.at n=16A246882