Orthogonality & Least Squares · Superchallenge problem

Let $A$ be the $4\times 3$ matrix with columns $(1,1,1,1)$, $(1,2,3,4)$, $(1,4,9,16)$, and let $A = QR$ be its QR factorization ($Q$ with orthonormal columns, $R$ upper triangular with positive diagonal). Find $R_{33}$.