188908910769domain: NAppears in sequencesSum of lists created by n substitutions k -> Range[k+1,0,-2] starting with {0}, counting down from k+1 to 0 step -2.at n=31A084081a(n) = (1/(2*n+1)) * Sum_{k=0..n} (k+1)^2 * (2*k+1) * binomial(3*n-k,n-k).at n=15A390968