467426domain: NAppears in sequencesTriangle T(n,k), 0<=k<=n, read by rows; given by [0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, ...] DELTA [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...] where DELTA is the operator defined in A084938.at n=62A094456Nullspace dimension of the periodic XX Heisenberg chain with n > 1 sites.at n=26A392387