310320

Appears in sequences

• Expansion of (1+x)^2/((1-2x)(1-3x)).at n=10A085277
• Triangle read by rows: T(n,k) = number of closed trails of length k starting and ending at a fixed vertex in the complete undirected graph on n labeled vertices, for n >= 1 and k = 0 .. n(n-1)/2.at n=51A357885