3. Pascal's triangle looks as follows: 1 2 1 1 3 3 1 1 4 6 4 1 The first entry in a row is 1 and the last entry is 1 (except for the first row which contains only 1), and every other entry in Pascal's triangle is equal to the sum of the two entries: the entry that is in the previous row and the same column, and the entry that is in the previous row and previous column