Make a Series

     What are the next three terms to the series?

1+ 3+ 7+ 15+ 31 + 63+ …………..

Answer: 127, 255, 511.

              This series is being built up according to the order where the actual term = 2n-1, with n being the number of term.

 Eg,

1^st Term = 2¹ - 1 = 2 -1 = 1

2^nd term   = 2²-1 = 4 -1 = 3

3^rd Term    = 2³ -1 = 8-1 = 7   

                         And so on