Hi Nasser,

I would prefer use of a special environment, like this:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% https://puszcza.gnu.org.ua/bugs/?624
\documentclass[12pt]{article}

\usepackage{amsmath}
\usepackage{longtable}
\usepackage{array}
\newcolumntype{C}{>{$}c<{$}}

\NewDocumentEnvironment{longmathtable}{m+b}{
\begin{longtable}{#1}
#2
\end{longtable}
}{}
\ifdefined\HCode
\RenewDocumentEnvironment{longmathtable}{m+b}{
\alteqtoks{\[\begin{array}{#1}
#2
\end{array}\]
}
}{}
\fi

\begin{document}

\begin{longmathtable}{CCC}
& {} & \textrm{Let's solve}
\\
{} & {} & \left[y^{\prime}=1+2 x , y \left(0\right)=3\right]
\end{longmathtable}

\end{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

I've defined a new column type, C, so you don't need to type all these ugly preambles, and also so it works better with MathJax. The redefined environment will print array in math mode.

This MWE compiles with no problem with lualatex but gives this error with tex4ht

---------------
(/usr/local/texlive/2023/texmf-dist/tex/latex/lm/t1lmtt.fd))
Runaway argument?
\b:array> \ignorespaces {} & \textrm {Let's solve} \\ {} & {} & \left \ETC.
! File ended while scanning use of \AltMathOne.
<inserted text>
\par
<*> ...=utf-8,html5.a.b.c.\input "\detokenize{A.tex}"

?
-----------------------

I am using code generated by Maple, and just putting this code inside longtable.

I can not change the code generated. Here is MWE. I only added the lines \begin{longtable}{...} and \end{longtable} and everything else in between is auto-generated.

-----------------------
\documentclass[12pt]{article}

\usepackage{amsmath}
\usepackage{longtable}
\usepackage{array}

\begin{document}

\begin{longtable}{ >{$}c<{$} >{$}c<{$} >{$}c<{$} }
& {} & \textrm{Let's solve}
\\
{} & {} & \left[y^{\prime}=1+2 x , y \left(0\right)=3\right]
\end{longtable}

\end{document}
--------------------------------

Now compiled using

make4ht -ulm default -a debug A.tex 'mathjax,htm'

and it gave the error shown above.

No error compiling with lualatex.

Using tex4ht under TL 2023

>which make4ht

/usr/local/texlive/2023/bin/x86_64-linux/make4ht

>make4ht --version

make4ht version v0.3m

How can I make this compile with tex4ht?

Thanks
--Nasser