2031252domain: NAppears in sequencesa(n) = Sum_{k = 0..n} C(n,k)^6.at n=5A069865Half the number of n X n binary matrices, symmetric under horizontal and vertical reflection, having equal row sums.at n=10A140453Constant term in the expansion of (Product_{k=1..n} (1 + x_k) + Product_{k=1..n} (1 + 1/x_k))^n.at n=5A328812