Seqeuncing

Find the next letters in the sequence (pretty tough):
O T T F F S S E _ _ _ _ _ _ _

Originally posted by prosoccer
Find the next letters in the sequence (pretty tough):
O T T F F S S E _ _ _ _ _ _ _

and then the most difficult part of the sequence:

T T T T T T T T T T T T T T T T T T T

Originally posted by Ian68
N T E T T F F S S E N T

Is that enough?

Okay, here is a difficult sequence:

c X c G G G G G G G G G G G G c

What's next?

Nobody?

Really? I have 79 posts to my 'Noone will solve it' thread, but noone wants to hazard a guess to my sequence, which CAN be solved!?