fix(curriculum): formatting on project euler 356 (#45312)

curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-356-largest-roots-of-cubic-polynomials.md

@@ -8,7 +8,7 @@ dashedName: problem-356-largest-roots-of-cubic-polynomials
 
 # --description--
 
-Let an be the largest real root of a polynomial $g(x) = x^3 - 2^n \times x^2 + n$.
+Let $a_n$ be the largest real root of a polynomial $g(x) = x^3 - 2^n \times x^2 + n$.
 
 For example, $a_2 = 3.86619826\ldots$