Thirty nines!
Number Theory
Level
3
What is the least positive integer \(n\) that can be placed in the following expression:
\[\large \color{red} n! (n+1)! (2n+1)! -1\]
and yields a number ending with thirty digits of 9's.
Notation: ! is a factorial notation; for example, \(8! = 8\times7\times6\times5\times4\times 3\times2\times1\)
by
Hana Nakkache