1622278624domain: NAppears in sequencesHalf the number of n X n binary matrices, symmetric under horizontal and vertical reflection, having equal row sums.at n=12A140453a(n) = Sum_{k = 0..n} C(n,k)^7.at n=6A182421Constant term in the expansion of (Product_{k=1..n} (1 + x_k) + Product_{k=1..n} (1 + 1/x_k))^n.at n=6A328812