2380405domain: NAppears in sequencesa(n) = Sum_{k=floor(n/4)..R} C(k, m*k - (-1)^n*(R - k)) * C(k + 1, m*(k + 2) - (-1)^n*(R - k + 1)) where m = (n + 1) mod 2 and R = (n + m - 3)/2 for n > 0 and a(0) = 1.at n=36A202411a(n) = Sum_{k=0..n} binomial(k-1,2*k-1-n)*binomial(k,2*k-n), with a(0) = 1.at n=18A203611