68518domain: NAppears in sequencesPartial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 531", based on the 5-celled von Neumann neighborhood.at n=41A272752G.f.: 1 + Sum_{n>=1} a(n)*x^n/(1 - x^n) = Product_{n>=1} (1 + x^n)/(1 - x^n).at n=27A300274