I'm not quite sure what you mean by "attract no numbers."
The Block-level elements section of @yihui's bookdown guide might be of help.
If you do not want a certain heading to be numbered, you can add {-} after the heading, e.g.,
# Preface {-}
I don't think you're writing a book, per se, but many of the same ideas apply. See also the Section numbering portion of the R Markdown HTML Documents guide: