Here is a surprising use of sequences to answer a counting question: how many license plates consist of 6 symbols, using only the three numerals 1, 2, and 3 and the four letters a, b, c, and d, so that no numeral appears after any letter? for example, "31ddac" and "12321" are acceptable license plates, but "13ba2c" is not. first answer this question by considering different cases: how many of the license plates contain no numerals? how many contain one numeral etc. a. b. now use the techniques of this section to show why the answer is 47 -37