There are 87 square numbers that use every digit (base 10, no leading zeroes)) exactly once.
List them.
(In reply to
Pencil and Paper solution (spoiler) by Steve Herman)
Why so many?
(10000010000*10^(1/2)) is the number of squares in the interval.
(9*9!/10000000000) is the ratio of pandigitals to all numbers in the interval.
(10000010000*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 20170415 23:44:09 