#OK to post homework 
#Zhizhang Deng, 09/22/2020, Assignment 3
1. 
2. 
NuFP:=proc(p) local i, res:   
res:=0:  
for i from 1 to nops(p) do    
    if p[i]=i then      
        res := res + 1: 
    fi:  
 od:  
 RETURN (res):  
 
 end;

 3. 
Der:=proc(n) local perms, i, res: 

perms := MyPerms(n):
res := {}:

for i in perms do: 
    if NuFP(i) = 0 then 
        res := {op(res), i}:
    fi:

od:
RETURN(res):
end:

4. 
It's a sequence of numbers that the permutations of this number of elements doesn't have any fixed points
Yes I can find it on OEIS
http://oeis.org/A000166

5. 
[seq(nops(Comps(i)),i=1..8)] = [1, 2, 4, 8, 16, 32, 64, 128]
Should be 2^(n-1)