Example OW.RECF.1 : $ f: N \rightarrow N$
$f(0)=1$ and $f(n+1)=(n+1) \times f(n)$.
Draw a mapping diagram and graph of $f$ yourself, or consider the GeoGebra figures and table below.
Martin Flashman, Dec. 21, 2013,
Created with GeoGebra
Notice how the points on the graph are paired with the points
on the mapping diagram.
Given a point / number, $n$, on the source line, there is a unique
arrow meeting the target line at the point / number, $f(n)$.
which corresponds to the function's value for $n$.
Click on the point marked $n$ in the mapping diagram and use the up
and down cursor controls on the keyboard to change the value of $n$
by $1$.
Click on a cell in column B of the spreadsheet to see how the number
in that cell is calculated by the recursion formula.