26615510712domain: NAppears in sequencesNumber of n X n symmetric binary matrices with all row sums 5.at n=5A139671Number of n X n 0..1 symmetric arrays with every row summing to floor(n/2).at n=10A213793Number of 2n X 2n symmetric matrices with entries in {+1, -1} and all rows and columns summing to zero.at n=5A333164