Which statement describes the sequence {1,3,7,15,…} as a mathematical statement? a the nth value equals 1 more than the sum of the previous value and n. b the nth value equals 1 more than twice the previous value. c the nth value equals the sum of the previous 3 values. d the nth value equals 1 more than twice the first value.

The answer is      b. the nth value equals 1 more than twice the previous value.  look at the 2nd value, which is 3.the previous value is 1. twice of 1 is 2; add one more gets you 3.look at the 3rd value, which is 7.previous value to 7 is 3. twice of 3 is 6; add one more gets you 7.look at the 4th value, which is 15.previous value to 15 is 7. twice of 7 is 14; add one more gets you 15.this pattern holds.