Let N be the largest number of region that can be formed by drawing 2016 straight lines on a plane. Find the sum of all digits of N.

I won't take credit for this solution, as it goes to this website: https://www.cut-the-knot.org/proofs/LinesDividePlane.shtml Applying 2016 to the formula, we'll get 2033137 regions, which has the sum of digit be 19

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