The numbers are increasing by 1,4,9,16,25,36.... which are square numbers so the next increase is 49. Making the next number in the sequence 141
Two possible answers spring immediately to mind. First, this sequence appears to be a list of the first five prime numbers; in this case, the next number in the sequence would be 13. Second, the intervals between these numbers comprise the sequence "1 2 2 4", in which the nth number equals the product of the (n-1)th and (n-2)th numbers. Based on this, the next number in the given sequence would be 11 + (4*2) = 19.
This list of numbers is the list of prime numbers. Following 11, the next two numbers in the list are 13 and 17.
The next number in the sequence would be 23. The sequence consists of prime numbers.
15... you're dividing by 2 each time.
13, 21 - it is the Fibonacci sequence
6 and 10
6, 2, ⅔
The next four number in the sequence are... 4,5,5 & 6
21. Add the last 2 numbers to get the next.
Fibonacci found a way to present mathematical numbers so that each number in the sequence is the sum of the two previous numbers. For example, if the sequence starts at 0 and 1, then next number in the sequence is 1, the next number would be 2, and then the next number would be 3, and then 5.
That's the Fibonacci sequence! XD They're 21 and 34 if you add up the last two numbers to get the next one.
It appears as if the pattern is doubling, therefore the next three numbers are 16, 32, and 64.
The next number is 70.The sequence is the central spine numbers of Pascal's Triangle (see related link and related question below).
These are all prime numbers. The next one is 17
8, if it is the Fibonacci sequence; 7, if it the sequence of non-composite numbers (1 and primes); there are other possible answers.