Find the missing term: 1, 9, 25, 49, ?, 121

The missing term is 81. This is a sequence of squares, so each number is the square of the next natural number. 1 is the square of 1, 9 is the square of 3, 25 is the square of 5, 49 is the square of 7, and 81 is the square of 9.