```
\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}
\begin{equation}
{S}=
\left(\begin{tabular}{1}
&\centering\{B_{M,i}\}\\
&\centering.\\
&\centering.\\
&\centering\{B_{1,i}\} \{B_{2,i}\} {.} {.} \{B_{M,i}\}
\end{tabular}
\right)
\end{equation}
\end{document}
```

When I execute the above code, I am getting the output, but it's stating "illegal character in an array arg".

## Best Answer

The "illegal character in

`array`

arg" references the fact that you're using`1`

as a column specification which is undefined. You can only use`l`

,`r`

,`c`

or`p{<len>}`

. Also, using`tabular`

places everything in text mode, which doesn't allow subscript/superscript without being in math mode. There is`array`

as a math alternative.Here's a suggested solution: