3 N ANTS
There are only two possibilities in which collision can be occurred.
Since every ant has two choices (pick either of two edges going through the corner on which ant is initially sitting). So for N ants there are total 2N possibilities.
Probability that none of the ants collide = ( 2 - 2)/ 2N
          = ( 2N-1   - 1)/ 2N-1
import math
# Non Collide Probability for N ANTS
# N Number of Ants & N > 2
N = 3
# P Probability
P = (math.pow(2,N-1)-1)/math.pow(2,N-1)
print('Probability that none of', N, 'ants collide:', P)
Output:
Probability that none of 3 ants collide: 0.75
If you set N = 4 then output:
Probability that none of 4 ants collide: 0.875
If you set N = 10 then output:
Probability that none of 10 ants collide: 0.998046875