7648032domain: NAppears in sequencesNumber of (n+1)X(n+1) 0..1 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.at n=6A187458T(n,k)=Number of (n+1)X(n+1) 0..k arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.at n=27A187462