Dr. Lizardo writes down a sequence of letters, where each letter is A, B, or C, and the letter A appears an even number of times. How many different sequences could Dr. Lizardo have written down?
+37165 How long is the sequence? Only 3 letters ? is ZERO A's considered a possibility?
AAx
AxA
xAA where x can be B or C 3 x 2 = 6 sequences
