AMC 10 Step by Step
2022 AMC 10BProblem 6P1-10~3 minPrint

How many of the first ten numbers of the sequence 121,11211,1112111,121, 11211, 1112111, \ldots are prime numbers?

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Problem © Mathematical Association of America (MAA), American Mathematics Competitions. Reproduced for non-commercial educational use. Solution and commentary are original to this site.