-2421

Appears in sequences

• (n+1)^2*a(n+1) = (9n^2+9n+3)*a(n) - 27*n^2*a(n-1), with a(0) = 1 and a(1) = 3.at n=6A006077
• First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 121", based on the 5-celled von Neumann neighborhood.at n=29A270209
• (n+1)^2*a(n+1) = -(9*n^2 + 9*n + 3)*a(n) - 27*n^2*a(n-1), with a(0) = 1 and a(1) = -3.at n=6A291898