11, 5, 20, 12, 40, 26, 74, 54

The given sequence is a combination of two series :

I. 11, 20, 40, 74 and II. 5, 12, 26, 54

The correct pattern in I is + 9, + 18, + 36,.....

So, 40 is wrong and must be replaced by (20 + 18) i.e. 38.