Two Column Layout for Tables

This is a solution utilizing nested tabular environments.

\documentclass[11pt]{article} 
\usepackage[utf8]{inputenc} 
\usepackage{xspace}
%% tables
\RequirePackage{array}
\RequirePackage{booktabs}
\RequirePackage{longtable, graphicx}
\usepackage{amsmath}[2000/07/18]
\gdef\Z{\phantom{0}}
\begin{document}
\small
\begin{tabular}{|l|c|}
\begin{tabular}[t]{rlr}
   C(\Z1) & = & 0.0000000000000+000 \\
   C(\Z2) & = & 5.0000000000000-001 \\     
   C(\Z3) & = & 0.0000000000000+000 \\
   C(\Z4) & = & 5.0000000000000-001 \\
   C(\Z5) & = & 0.0000000000000+000 \\
   C(\Z6) & = & 5.0000000000000-001 \\     
   C(\Z7) & = & 0.0000000000000+000 \\
   C(\Z8) & = & 5.0000000000000-001 \\
   C(\Z9)  & = & 0.0000000000000+000 \\
   C(10) & = & 5.0000000000000-001 \\  

\end{tabular}&
\begin{tabular}[t]{rlll}

   C(11) & = & 0.0000000000000+000 \\
   C(12) & = & 5.0000000000000-001 \\
   C(13) & = & 0.0000000000000+000 \\
   C(14) & = & 5.0000000000000-001 \\     
   C(15) & = & 0.0000000000000+000 \\
   C(16) & = & 5.0000000000000-001 \\ 
   C(17) & = & 5.0000000000000-001 \\   
   C(18) & = & 5.0000000000000-001 \\
   C(19) & = & 5.0000000000000-001 \\
   C(20) & = & 5.0000000000000-001 \\
\end{tabular}
\end{tabular}
\end{document}

If you generating the coefficients programmatically you will need to device some means for paging. You can also improve on the code above which I kept as simple as possible for clarity by using formatting commands to align the decimal and the sign of the numbers. I have used a macro \Z that uses \phantom to align the numbers in C( 1) with C(10).

use the tabbing environment instead of a longtable. It can be set in a \twocolumnmode. The first line is killed after defining the tabstops. However, if you can set all lines in \ttfamily, then you need nothing, all will be fine. Alternatively put the first "C(..) = " in a box of a fixed width. The it is also formatted, because all digits are of the same width.

\documentclass[11pt]{article} 
\usepackage[utf8]{inputenc} 
\textheight=5cm
\def\Z{\phantom{0}}
\begin{document}
\twocolumn

\small\ttfamily
\begin{tabbing}
   C(10) \== \=5.0000000000000-001 \\\kill   
   C(\Z1) \>=\> 0.0000000000000+000 \\
   C(\Z2) \>=\> 5.0000000000000-001 \\     
   C(\Z3) \>=\> 0.0000000000000+000 \\
   C(\Z4) \>=\> 5.0000000000000-001 \\
   C(\Z5) \>=\> 0.0000000000000+000 \\
   C(\Z6) \>=\> 5.0000000000000-001 \\     
   C(\Z7) \>=\> 0.0000000000000+000 \\
   C(\Z8) \>=\> 5.0000000000000-001 \\
   C(\Z9)  \>=\> 0.0000000000000+000 \\
   C(10) \>=\> 5.0000000000000-001 \\  
   C(11) \>=\> 0.0000000000000+000 \\
   C(12) \>=\> 5.0000000000000-001 \\
   C(13) \>=\> 0.0000000000000+000 \\
   C(14) \>=\> 5.0000000000000-001 \\     
   C(15) \>=\> 0.0000000000000+000 \\
   C(16) \>=\> 5.0000000000000-001 \\ 
   C(17) \>=\> 5.0000000000000-001 \\   
   C(18) \>=\> 5.0000000000000-001 \\
   C(19) \>=\> 5.0000000000000-001 \\
   C(20) \>=\> 5.0000000000000-001 \\
\end{tabbing}
\end{document}