32680domain: NAppears in sequencesa(n) = (n^4 + n^2 + 2*n)/4.at n=19A006528T(n, k) = Sum_{i=0, n} (Sum_{j=0, k} C(i+j,i) * C(n-i+j,n-i) * C(i+k-j,k-j) * C(n-i+k-j,n-i)).at n=49A186753T(n, k) = Sum_{i=0, n} (Sum_{j=0, k} C(i+j,i) * C(n-i+j,n-i) * C(i+k-j,k-j) * C(n-i+k-j,n-i)).at n=50A186753