Question

What is the pattern rule for 1/3,7,15?

Answer 1

That is, each subsequent element in the series is the previous element plus 2^(n-1) where n is the sequence number of the element. So the series is then: 1, 3, 7, 15, 15+2^4, 15+2^4+2^5 and so on. Or: 1, 3, 7, 15, 31, 63, 127, 255, ….