A die is rolled 13 times. What is the probability of at least two 6's appearing? (Round your answer to four decimal places.)
2. The attempt at a solution
I know that the total number of outcomes is 6^13. I did (13nCr2)x(1x1x6x6x6x6x6x6x6x6x6x6x6)/6^13, but the answer isn't right. What am I doing wrong?