Can someone figure out the pattern? Each number always maps to another number, eventually getting to 4.
$1 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$2 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$3 \Rightarrow 5 \Rightarrow 4$
$4$
$5 \Rightarrow 4$
$6 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$7 \Rightarrow 5 \Rightarrow 4$
$8 \Rightarrow 5 \Rightarrow 4$
$9 \Rightarrow 4$
$10 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$11 \Rightarrow 6 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$12 \Rightarrow 6 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
$13 \Rightarrow 8 \Rightarrow 5 \Rightarrow 4$
$14 \Rightarrow 8 \Rightarrow 5 \Rightarrow 4$
$15 \Rightarrow 7 \Rightarrow 5 \Rightarrow 4$
$16 \Rightarrow 7 \Rightarrow 5 \Rightarrow 4$
$17 \Rightarrow 9 \Rightarrow 4$
$18 \Rightarrow 8 \Rightarrow 5 \Rightarrow 4$
$19 \Rightarrow 8 \Rightarrow 5 \Rightarrow 4$
$20 \Rightarrow 6 \Rightarrow 3 \Rightarrow 5 \Rightarrow 4$
