回复：A General Solution

来源: fzy 于 2005-02-07 07:48:07 [] [旧帖] [给我悄悄话] 阅读数 : (287 bytes)
回答: 90909090910^2 由 fzy 于 2005-02-06 17:05:54

I believe x=(10^k+1)*p^2/q^2 is the general formula. Here we need

1) (10^k+1) mod q^2 = 0
2) 0.1
2) is needed to make x a k digit number, and I chose p = 10. You can also choose p = 4 to 9.

The key is how to find k and q. It is only easy for q = 11.

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