Primalité

20
1 20
12345
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
2 4 8
1235
79
11 13 15
17 19 
1
3 3
1235
7  
11 13  
17 19 

5
20
n
2n−1 2 b√nc
p a ∈Z
ap−1≡1p
24≡1 5 34≡1 5
an−16= 1 n n
29≡2 10 10
C
561 a∈Z
aC−1≡1C
1994
n
C
ap−1≡1p
a

p
x2≡1p
(x−1) ×(x+ 1) ≡0p
p1−1
n n −1 2s×d
r < s
xd≡1p
x2sd≡ −1p
xd6= 1 n
x2rd6=−1n
x
r < s