A multi-column table with row auto-numbering

Question

How can I build a table in several columns so that the numbering is automatic and the values in the table header are not numbered. You need to get a table in accordance with the figure

    \documentclass[a4paper,12pt]{article}
\usepackage{cmap} 
\usepackage[T2A]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,russian]{babel} 
\usepackage{caption}
\usepackage{multirow}
\usepackage{array,etoolbox}
\usepackage{tikz}

\usepackage{siunitx}
\usepackage{nicematrix}

\usetikzlibrary{calc,angles,positioning,intersections,quotes,decorations.markings}
\usepackage{tkz-euclide}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage[skip=1ex]{subcaption}

\usepackage{multicol}
\begin{document}
    \newcounter{rownum} 
    \setcounter{rownum}{-1}
    \newcommand{\Rownum}{\stepcounter{rownum} \ifnum\value{rownum}>0\relax\arabic{rownum}\fi }  

    \begin{table}[ht]
        \centering 
        \ExplSyntaxOn
        \NewDocumentCommand \BackgroundColors { }
        {
            \begin{tikzpicture}
                \begin{scope}
                    \clip [rounded~corners] (1-|1) rectangle (last-|last) ;
                    \fill [gray!40] (1-|1) rectangle (2-|last) ; 
                    \foreach \i in {3,5,7,...,\arabic{iRow}}
                    { \fill [gray!20] (\i-|1) rectangle (\int_eval:n{\i+1}-|last) ; }
                \end{scope}
                \draw [rounded~corners,gray!80] (1-|1) rectangle (last-|last) ; 
            \end{tikzpicture}
        }
        \ExplSyntaxOff
        \renewcommand{\arraystretch}{1.5}
        
        \begin{multicols}{2}
        \begin{NiceTabular}{>{\Rownum}cc}
            \CodeBefore
            \BackgroundColors
            \Body
            \RowStyle[bold]{}
            {\textnumero} & {F, MHz} \\
            & 433,075 \\
            & 433,100 \\
            & 433,125 \\
            & 433,155 \\
            & 433,175 \\
            & 433,200 \\    
            & 433,225 \\
            & 433,255 \\        
        \end{NiceTabular}
        \columnbreak
            \begin{NiceTabular}{>{\Rownum}cc}
        \CodeBefore
        \BackgroundColors
        \Body
        \RowStyle[bold]{}
        {\textnumero} & {F, MHz} \\
        & 433,075 \\
        & 433,100 \\
        & 433,125 \\
        & 433,155 \\
        & 434 \\
        & 435 \\    
        & 436 \\
        & 437 \\        
    \end{NiceTabular}
    \end{multicols}
    \end{table}

\end{document}

Answer 1

This is probably not the most elegant way to do this, but you can use a custom conditional that is set to false before the table header is typeset and then set to true via tha \Rownum macro. This will skip typesetting of the row number for the first row:

\documentclass[a4paper,12pt]{article}
\usepackage[english,russian]{babel} 
\usepackage{tikz}
\usepackage{nicematrix}
\usetikzlibrary{calc,angles,positioning,intersections,quotes,decorations.markings}
\usepackage{multicol}

\begin{document}
    \newcounter{rownum} 
    \setcounter{rownum}{0}
    \newif\ifheadrow
    \newcommand{\Rownum}{\ifheadrow\stepcounter{rownum}\arabic{rownum}\fi}  

    \begin{table}[ht]
        \centering 
        \ExplSyntaxOn
        \NewDocumentCommand \BackgroundColors { }
        {
            \begin{tikzpicture}
                \begin{scope}
                    \clip [rounded~corners] (1-|1) rectangle (last-|last) ;
                    \fill [gray!40] (1-|1) rectangle (2-|last) ; 
                    \foreach \i in {3,5,7,...,\arabic{iRow}}
                    { \fill [gray!20] (\i-|1) rectangle (\int_eval:n{\i+1}-|last) ; }
                \end{scope}
                \draw [rounded~corners,gray!80] (1-|1) rectangle (last-|last) ; 
            \end{tikzpicture}
        }
        \ExplSyntaxOff
        \renewcommand{\arraystretch}{1.5}
        
        \begin{multicols}{2}
        \begin{NiceTabular}{>{\Rownum\global\headrowtrue}cc}
            \CodeBefore
            \BackgroundColors
            \Body
            \RowStyle[bold]{}
            {\textnumero} & {F, MHz} \\
            & 433,075 \\
            & 433,100 \\
            & 433,125 \\
            & 433,155 \\
            & 433,175 \\
            & 433,200 \\    
            & 433,225 \\
            & 433,255 \\        
        \end{NiceTabular}
        \columnbreak
        \global\headrowfalse
        \begin{NiceTabular}{>{\Rownum\global\headrowtrue}cc}
            \CodeBefore
            \BackgroundColors
            \Body
            \RowStyle[bold]{}
            {\textnumero} & {F, MHz} \\
            & 433,075 \\
            & 433,100 \\
            & 433,125 \\
            & 433,155 \\
            & 434 \\
            & 435 \\    
            & 436 \\
            & 437 \\        
        \end{NiceTabular}
        \end{multicols}
    \end{table}

\end{document}

---

You probably want to use multiple counters to be able to combine the different table columns into one single table:

\documentclass[a4paper,12pt]{article}
\usepackage[english,russian]{babel} 
\usepackage{tikz}
\usepackage{nicematrix}
\usetikzlibrary{calc,angles,positioning,intersections,quotes,decorations.markings}
\usepackage{multicol}

\newcommand{\RownumCols}[2]{
    \newif\ifheadrow
    \global\headrowfalse
    \foreach \i in {1,...,#2} {
        \pgfmathparse{int(\i * #1 / #2 - #1 / #2)}
        \newcounter{rownum\romannumeral\i}
        \setcounter{rownum\romannumeral\i}{\pgfmathresult}
    }
}
\newcommand\Rownum[1]{
    \ifheadrow\stepcounter{rownum\romannumeral#1}\arabic{rownum\romannumeral#1}\fi
}

\begin{document}

    \begin{table}[ht]
        \centering 
        \ExplSyntaxOn
        \NewDocumentCommand \BackgroundColors { }
        {
            \begin{tikzpicture}
                \begin{scope}
                    \clip [rounded~corners] (1-|1) rectangle (last-|last) ;
                    \fill [gray!40] (1-|1) rectangle (2-|last) ; 
                    \foreach \i in {3,5,7,...,\arabic{iRow}}
                    { \fill [gray!20] (\i-|1) rectangle (\int_eval:n{\i+1}-|last) ; }
                \end{scope}
                \draw [rounded~corners,gray!80] (1-|1) rectangle (last-|last) ; 
            \end{tikzpicture}
        }
        \ExplSyntaxOff
        \renewcommand{\arraystretch}{1.5}
        
        \RownumCols{16}{2}
        
        \begin{NiceTabular}{>{\Rownum{1}}cc >{\Rownum{2}\global\headrowtrue}cc}
            \CodeBefore
            \BackgroundColors
            \Body
            \RowStyle[bold]{}
            {\textnumero} & {F, MHz} & {\textnumero} & {F, MHz} \\
            & 433,075 & & 433,075 \\
            & 433,100 & & 433,100 \\
            & 433,125 & & 433,125 \\
            & 433,155 & & 433,155 \\
            & 433,175 & & 434 \\
            & 433,200 & & 435 \\    
            & 433,225 & & 436 \\
            & 433,255 & & 437 \\        
        \end{NiceTabular}
    \end{table}

\end{document}

The macro \RownumCols{16}{2} takes the maximum count of entries and the number of columns. It sets up the needed counters that are already initialized with the correct starting value. You can access the value of these counters by using \Rownum{1} or \Rownum{2}.