347916domain: NAppears in sequencesNumber of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n+1, n or n-1 exactly once.at n=9A270852G.f. A(x) satisfies 2*x = Sum_{n=-oo..+oo} (-1)^n * x^(2*n) * (A(x) + x^n)^(2*n) with A(0) = 1.at n=9A380681