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 Pandigital and square (Posted on 2017-04-15)
There are 87 square numbers that use every digit (base 10, no leading zeroes)) exactly once.

List them.

 No Solution Yet Submitted by Ady TZIDON No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
 re: Pencil and Paper solution (spoiler) | Comment 3 of 6 |
(In reply to Pencil and Paper solution (spoiler) by Steve Herman)

Why so many?

(100000-10000*10^(1/2)) is the number of squares in the interval.

(9*9!/10000000000) is the ratio of pan-digitals to all numbers in the interval.

(100000-10000*10^(1/2))*(9*9!/10000000000)=22.331, not 87.

In particular, why should there be almost exactly 4 times as many (or is that simply a coincidence)?

 Posted by broll on 2017-04-15 23:44:09

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