Derangements (no fixed point permutations) (D_n = count of permutations of n items where no item keeps its original)
jee-mainjee-advanced
D_n = count of permutations of n items where no item keeps its original place
What each symbol means
| Symbol | What it stands for |
|---|---|
| n | Size of set |
| D_n | Number of derangements of n labelled objects |
When to use this
D_0=1 (empty permutation), D_1=0, D_2=1, D_3=2, D_4=9.