Hi guys, first time poster. I hope this section is the most appropriate for my problem - please feel free to move it if it is too basic

A fair coin is flipped n times.

What is the probability that there are at least k consecutive heads in these flips?

If the k-generalisation is making the working awkward then please just solve it for k = 2 because I think I know how to get from there to the general answer.

Thanks for any help you can give me!