AoPS Wiki:Problem of the Day/July 6, 2011
Find the sum $1+11+\cdots+\underbrace{111\cdots 111}_{n}}$ (Error compiling LaTeX. ! Extra }, or forgotten $.).
Find the sum $1+11+\cdots+\underbrace{111\cdots 111}_{n}}$ (Error compiling LaTeX. ! Extra }, or forgotten $.).