On sufficient conditions for the total positivity and for the multiple   positivity of matrices
  The following theorem is proved:   Suppose $M = (a_{i,j})$ be a $k \times k$ matrix with positive entries and $a_{i,j}a_{i+1,j+1} > 4\cos ^2 \frac{\pi}{k+1} a_{i,j+1}a_{i+1,j} \quad (1 \leq i \leq k-1, 1 \leq j \leq k-1).$ Then $\det M > 0 .$ The constant $4\cos ^2 \frac{\pi}{k+1}$ in this Theorem is sharp. A few other results concerning totally positive and multiply positive matrices are obtained.   Keywords: Multiply positive matrix; Totally positive matrix; Strictly totally positive matrix; Toeplitz matrix; Hankel matrix; P\'olya frequency sequence. 
Olga M. Katkova, Anna M. Vishnyakova