20060016

Appears in sequences

• Number of 2n-bead black-white reversible strings with n black beads.at n=14A032123
• Central column of Losanitsch's triangle A034851.at n=28A034872
• a(n) = (1/2)*(binomial(4*n, 2*n) - (-1)^n*binomial(2*n,n)).at n=7A037964
• a(n) = Sum_{k=0..n} C(n,k)^2*mod(k,2).at n=14A110145