If probability of an event happening is p, then the probability that the event happens n times in a row is p∧n.
The probability that a coin toss results in head is 0.5. Then the probability that when the coin is tossed twice, both of them are head is 0.5∧2=0.25.
Probability that a roll of a six-sided die land with face 1 is 1/6. Then the probability that 1 will turn up three times in a row is (1/6)∧3.
Note that probability of the event happening does not change from trial to trial.