1 , 3 , 4 , 7 , 11 ,18 , 27 , 47

As per the details in the question the series is in the form of
The sum of the first two nos. is the third no.
? First term + Second term = Third term
? 1 + 3 = 4 ;
Second term + Third term = Fourth term
? 3 + 4 = 7 ;
Third term + Fourth term = Fifth term
? 4 + 7 = 11 ;
Fourth term + Fifth term = Sixth term
? 7 + 11 = 18 ;
Fifth term + Sixth term = Seventh term
? 11 + 18 = 27 is wrong. It should be 29.
Sixth term + Seventh term = Eighth term
? 18 + 29 = 47
Hence, 27 is wrong. It should be 29.