1,9,25,49,_

1 answer

The pattern in this sequence is the square of consecutive odd numbers.

1 = 1^2
9 = 3^2
25 = 5^2
49 = 7^2

Following this pattern, the next number in the sequence would be the square of the next odd number, which is 9. Therefore, the missing number is 81.

81 = 9^2