3,5,8,13 is followed by 21.
1,1,2,3,5,8,13,21,34,55,... is the Fibonacci series or Fibonacci sequence where the next number in the sequence is the sum of the last two numbers (1+1=2, 1+2=3, 2+3=5, etc.)
The sequence alternates between a number and that number plus one. After 2 comes 3, after 3 comes 12, after 12 comes 13, after 13 comes 52, and after 52 comes 53. Following this pattern, the next number after 53 would be 212, as it follows 52 multiplied by 4 (the previous non-incrementing number). Therefore, the next number in the sequence is 212.
17 cause it is the next prime number
18. 3+1=4, 4+2=6, 6+3=9, 9+4=13, 13+5=18.
The next number is 13... you're adding the previous two numbers together to produce the next in line.
The pattern alternates between two sequences: one decreasing by 1 (18, 13) and the other decreasing by 2 (4, 6). Following this pattern, the next number after 6 should be 3 (6 - 3), and the next number after 13 should be 12 (13 - 1). Thus, the next two numbers in the sequence are 12 and 3.
The sequence alternates between a number and that number plus one. After 2 comes 3, after 3 comes 12, after 12 comes 13, after 13 comes 52, and after 52 comes 53. Following this pattern, the next number after 53 would be 212, as it follows 52 multiplied by 4 (the previous non-incrementing number). Therefore, the next number in the sequence is 212.
18
17 cause it is the next prime number
31
the next number is 21 because it is adding the last number stated.
17
34
13, because if you add the last number to the current number you get the next number
18. 3+1=4, 4+2=6, 6+3=9, 9+4=13, 13+5=18.
13 because each time it goes 1 odd number up.
The next number is 13... you're adding the previous two numbers together to produce the next in line.
These are Fibannoci's numbers. Therefore, the 7th number is 21.