Find the number of sequences (a_1, a_2, a_3, \dots, a_8) such that: * a_i \in \{1, 2, 3, 4, 5, 6, 7, 8\} for all 1 \le i \le 8. * Every number1, 2, 3, 4, 5, 6, 7, 8 appears at least once in the sequence.
+400 
