15. (Hu-Li-Zhan) 秩为 $k$ 的 $n$ 阶对称 $0-1$ 矩阵中 $1$ 的个数可能是哪些数呢?
解答: 见 [Q. Hu, Y.Q. Li, X.Z. Zhan, Possible numbers of ones in $0-1$ matrices with a given rank, Linear Multilinear Algebra, 53 (2005), 435--443].
15. (Hu-Li-Zhan) 秩为 $k$ 的 $n$ 阶对称 $0-1$ 矩阵中 $1$ 的个数可能是哪些数呢?
解答: 见 [Q. Hu, Y.Q. Li, X.Z. Zhan, Possible numbers of ones in $0-1$ matrices with a given rank, Linear Multilinear Algebra, 53 (2005), 435--443].