121873

Appears in sequences

• a(n) = 1 - 2*n^2 + 4*n*(1 + 2*n^2)/3.at n=36A168547
• Triangle read by rows: T(n,k) is the number of weighted lattice paths in B(n) having k ascents. The members of B(n) are paths of weight n that start at (0,0), end on but never go below the horizontal axis, and whose steps are of the following four kinds: an (1,0)-step with weight 1, an (1,0)-step with weight 2, a (1,1)-step with weight 2, and a (1,-1)-step with weight 1. The weight of a path is the sum of the weights of its steps. An ascent is a maximal sequence of consecutive (1,1)-steps.at n=60A246186
• Number of irredundant sets in the n-ladder graph.at n=10A290513