Number of rolls until the same number appears 2 consecutive times

Question

I don't think the formula given here: Expected number of rolls until a number appears $k$ times is correct. For example what's the expected number of rolls before two consecutive 6's -- 66? It should be 42, not 7, as their formula suggests. The number 42 can be easily calculated using Wald's identity and the smoothing property (6 + 1 = 7 and, then, 7 * 6 = 42). Can someone explain what's going on?

Answer 1

The answer for the question you linked specifies the expected number of rolls to get any number $k$ times, which is $7$ for $k=2$, while the problem you refer to is the expected number of rolls to get a particular number $k$ times, here $6$, which is $42$ for $k=2$. This intuitively seems correct as well because $42=6\times7$, and you have $6$ possible numbers on a die.