26991

Appears in sequences

• a(n) = (1+n)*(9 + 11*n + 4*n^2)/3.at n=26A172482
• Expansion of e.g.f. exp(x+x^2-1/6*x^3).at n=10A200380
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 809", based on the 5-celled von Neumann neighborhood.at n=29A273612