AAA <math>...
C n f ( n ) = { n / 2 , if n is even 3 n + 1 , if n is odd {\displaystyle \mathbb {C} ^{n}f(n)={\begin{cases}n/2,&{\text{if }}n{\text{ is even}}\\3n+1,&{\text{if }}n{\text{ is odd}}\end{cases}}}
BBB <math display="block">...
CCC :<math>...
DDD