A=\left[\matrix{%
 a_{11}& a_{12}& a_{13}&\dots&a_{1n} \cr
 a_{21} & a_{22} & a_{23} &\dots & a_{2n} \cr
 . & . &.& .&. \cr
. & . & . & .&.\cr
 a_{n1}  & a_{n2} & a_{n3}& \dots & a_{nn}}\right]