Data Sufficiency (DS) | Re: In a sequence of numbers in which each term after the first term is 1

I think the answer would be E?

Using a linear equation of 2X + 1 = Y
Term 1: X = 1, Y = 3
Term 2: X = 3, Y = 7
Term 3: X = 7, Y = 15
Term 4: X = 15, Y = 31
Term 5: X = 31, Y = 63
Term 6: X = 63, Y = 127

127 - 63 = 64

---