MathDB

The paper is written on consecutive integers

1

through

n

. Then are deleted all numbers ending in

4

and

9

and the rest alternating between

-

and

+

. Finally, an opening parenthesis is added after each character and at the end of the expression the corresponding number of parentheses:

1 - (2 + 3 - (5 + 6 - (7 + 8 - (10 +...))))

. Find all numbers

n

such that the value of this expression is

13

Problem Statement