> For the complete documentation index, see [llms.txt](https://mandober.gitbook.io/math-debrief/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mandober.gitbook.io/math-debrief/600-toc/632-recursive-function-theory/sudan-function.md).

# Sudan function

<https://en.wikipedia.org/wiki/Sudan\\_function>

The Sudan function is an example of a function that is recursive, but not primitive recursive. The Sudan function was the first function having this property to be published. It was discovered and published in 1927 by Gabriel Sudan, a Romanian mathematician who was a student of David Hilbert.