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 Excellent numbers (Posted on 2017-04-08)
An excellent number n has an even number of digits and, if you split the number into the front half a and the back half b, then b^2 − a^2 = n.
For example, 3468 = 68^2 − 34^2.
The only two-digit excellent number is 48 and the only four-digit
excellent number is 3468.

There are eight six-digit excellent numbers.

List them.

Bonus: List all 10-digit excellent numbers.

Source: Project Euler.

 No Solution Yet Submitted by Ady TZIDON No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
 computer solution: 6-, 8- and 10-digits | Comment 1 of 3
140400
190476
216513
300625
334668
416768
484848
530901
16604400
33346668
59809776
3333466668
4848484848
4989086476

from

Dim crlf\$

Form1.Visible = True

Text1.Text = ""
crlf = Chr\$(13) + Chr\$(10)

For i = 100000 To 999999
i2 = i Mod 1000
i1 = (i - i2) / 1000
If i2 * i2 - i1 * i1 = i Then Text1.Text = Text1.Text & i & crlf
DoEvents
Next

For i = 10000000 To 99999999
i1 = Int(i / 10000)
i2 = i - 10000 * i1
If i2 * i2 - i1 * i1 = i Then Text1.Text = Text1.Text & i & crlf
DoEvents
Next

For i = 1000000000 To 9999999999#
i1 = Int(i / 100000)
i2 = i - 100000 * i1
If i2 * i2 - i1 * i1 = i Then Text1.Text = Text1.Text & i & crlf
DoEvents
Next

Text1.Text = Text1.Text & crlf & " done"

End Sub

 Posted by Charlie on 2017-04-08 12:17:11

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