Autonum.info -

Compile twice. Result: Equation (1) has a number, equation (2) has no number. autonum is a powerful, time-saving package for authors who want their equation numbering to be driven by content references rather than manual decisions. It integrates seamlessly with standard math environments and reference packages, making it an excellent choice for technical documents of any length. The only requirement is a habit of compiling twice (or using latexmk ) – a small price for fully automated numbering hygiene. Further information : Full documentation is available on autonum.info or by running texdoc autonum in your TeX distribution.

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% This equation will be numbered because it is referenced below \beginequation E = mc^2 \labeleq:einstein \endequation autonum.info

\beginequation g(x) = \sqrtx \labeleq:root \endequation Compile twice

We only refer to \eqrefeq:first. Hence only the first line gets a number. It integrates seamlessly with standard math environments and

Compile twice. Result: Equation (1) has a number, equation (2) has no number. autonum is a powerful, time-saving package for authors who want their equation numbering to be driven by content references rather than manual decisions. It integrates seamlessly with standard math environments and reference packages, making it an excellent choice for technical documents of any length. The only requirement is a habit of compiling twice (or using latexmk ) – a small price for fully automated numbering hygiene. Further information : Full documentation is available on autonum.info or by running texdoc autonum in your TeX distribution.

\enddocument

% This equation will be numbered because it is referenced below \beginequation E = mc^2 \labeleq:einstein \endequation

\beginequation g(x) = \sqrtx \labeleq:root \endequation

We only refer to \eqrefeq:first. Hence only the first line gets a number.