21201211

Appears in sequences

• Expansion of (2/(3*sqrt(1-4*z)-1+4*z))*((1-sqrt(1-4*z))/(2*z))^k with k=4.at n=12A172061
• Number of 6Xn 0..1 arrays with rows unimodal and columns nondecreasing.at n=15A225013