Question 1143692
<pre>
The number of odd digits in 18 is 1, subtract 1 from 1, get 0.
the number of odd digits in 19 is 2, subtract 2 from 2, get 0.
the number of odd digits in 20 is 0, subtract 0 from 3, get 3.
the number of odd digits in 21 is 1, subtract 1 from 4, get 3.
the number of odd digits in 22 is 0, subtract 0 from 5, get 5.
the number of odd digits in 23 is 1, subtract 1 from 6, get 5.
the number of odd digits in 24 is 0, subtract 0 from 7, get 7.
the number of odd digits in 25 is 1, subtract 1 from 8, get 7.
the number of odd digits in 26 is 0, subtract 0 from 9, get 9.
the number of odd digits in 27 is 1, subtract 1 from 10, get 9.

So you have to find an explicit formula for the number of odd
digits in an integer.  Do you know of one?

Edwin</pre>




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