43863

Appears in sequences

• Triangle read by rows: T(n,k) is the number of unlabeled directed graphs on n nodes with k arcs, k=0..n*(n-1).at n=56A052283
• Triangle read by rows: T(n,k) is the number of unlabeled directed graphs on n nodes with k arcs, k=0..n*(n-1).at n=66A052283
• Expansion of 2/((x+3)*sqrt(-3*x^2-2*x+1)+3*x^2+2*x-1).at n=12A189832
• a(n) = (3/n^3) * Sum_{d|n} (-1)^(n+d)*moebius(n/d)*binomial(2*d,d).at n=13A254593