這是OG11 DS 101題:
If S is the infinite sequence S1=9,S2=99,S3=999,...,Sk=(10的k次方)-1,..., is every term in S divisible by the prime number p?
(1) p is greater than 2.
(2) At least one term in sequence S is divisible by p.
不太瞭解題目要的是什麼,有人可以解釋嗎?尤其是(2),
謝謝!