If the set of all \( a \in \mathbb{R} \), for which the equation \( 2x^2 + (a-5)x + 15 = 3a \) has no real root, is the interval \( (\alpha,\beta) \), and \( X = \{ x \in \mathbb{Z} : \alpha < x < \beta \} \), then \( \sum\limits_{x \in X} x^2 \) is equal to:
