579168825domain: NAppears in sequencesa(n) = Sum_{k=0..n-1} binomial(n,k+1) * binomial(n+k,k).at n=13A002002a(n) = T([n/2],[(n+1)/2]), where T = Delannoy triangle (A008288).at n=25A026003Expansion of (1 + x)^12 / (1 - x)^13.at n=13A053805