We have just shown that some numbers stay unchanged when a number of mathematical operators are added /inserted, without changing the order of the digits.
Within our puzzle lets call those numbers expressionist numbers.
Let us limit the set of acceptable mathematical symbols to the following operators: +, -, *, /, ^, sqrt, !. and any amount of brackets.

My questions:
In the period between 10 A.D. & 2016 A.D. what years were labeled by expressionist numbers?
How many such years will there be between 2017 A.D. & 9999 A.D.?

Bonus: How about one, two (or more) 5-digit examples?

In addition to the limitations previously mentioned about no more that two square roots in a row and precision limitations, etc. there's also the fact that I didn't allow for starting any formula with a leading negative sign, so that for example 9-1 could be written as -1 + 9 (not that these satisfy what the puzzle asks for; it's only an example).

Posted by Charlie on 2016-05-31 07:39:57