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Squares built from leftovers (Posted on 2018-04-05) Difficulty: 2 of 5
Let N1=123456789
Erase n digits and shrink the remnants of N1 into one continuous chain creating a new number N1'.

What is the minimum number of digits to be erased so that N1' will be a square number?

Same question for N2=987654321 and N2'.

See The Solution Submitted by Ady TZIDON    
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Solution by cheating | Comment 2 of 4 |
If you consider looking up the numbers on OEIS to be cheating.
I found the numbers up to 3 digits then searched and found
The largest number is 134689, three digits erased
The largest number is 961, six digits erased. 
(I'm surprised at having to erase so many.) 

Edited on April 5, 2018, 2:54 pm
  Posted by Jer on 2018-04-05 14:33:51

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