Find all n≥2 such that the polynomial xⁿ-x^n-1-x^n-2-…-x-1 is irreducible over the rationals.

The best solution was submitted by Gee Won Suh (서기원), 수리과학과 2009학번. Congratulations!

Here is his Solution of Problem 2011-19.

One incorrect solution by W.J. Kim was submitted.