21977516

Appears in sequences

• Number of log-concave paths of length n starting from the origin (0,0) with steps from {N=(0,1), E=(1,0) and S=(0,-1)} that stay in the second octant and never touch the line y=x except possibly at the beginning or the end.at n=26A079280
• Expansion of (sqrt(1 - 4*x) + (1 - 2*x))/(2*(1 - 4*x)).at n=13A114121
• Expansion of ((1 + x - 2x^2) + (1+x)*sqrt(1-4x^2))/(2(1-4x^2)).at n=26A116406
• Number of walks of length n starting at origin and ending in first quadrant on a square lattice.at n=13A187151
• a(n) = Sum_{k=0..13} binomial(n, k).at n=25A219676