G
C
This is the prime numbers: O = 1 T = 3 F = 5 S = 7 E = 11 T = 13 S = 17 One has been included although not being prime. Two has been left out although prime. The next prime number after 17 is 19, and so the next letter would be N.
It looks as if every third letter is an "r"; the remaining letters are in sequence.
Assuming that you want the numbers that contain the letter 'o' the answer is 22.
e
G
c
m
E
Hey, no cheating!
E. Eight.
The sequence is following the order of the vowels in the alphabet. Next would be i (after e), then o (after u), and so on.
C
SEOCNODEJAFE SE---September OC---October NO---November DE---December JA---January FE---February The next sequence will be FE for February.
I
h