Excess Kurtosis of Pareto Distribution/Lemma 2

Lemma for Excess Kurtosis of Pareto Distribution

 * $4 a \paren {a - 1}^3 \paren {a - 2}^2 \paren {a - 4} = 4 a^7 - 44 a^6 + 188 a^5 - 404 a^4 + 464 a^3 - 272 a^2 + 64 a$