I know the number of normal subgroup in $D_3$ and $D_4$ but I don't know the number of normal subgroup of rest of the Dihedral group like $D_{16}$ or $D_{60}$. I want to know is there any formula for finding number of normal subgroup in $D_n$. If there is no formula for that then how could we able to find that as I'm a beginner please help.
Interesting property of dihedral group
1
$\begingroup$
abstract-algebra
group-theory
normal-subgroups
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0duplicate of (http://math.stackexchange.com/q/484828) – 2017-02-01