AB is a sequence of numbers. When a equals 3 579, B is 5 913 17. When a equals 117, how much is B

AB is a sequence of numbers. When a equals 3 579, B is 5 913 17. When a equals 117, how much is B

When a equals 3 5 7 9, B is 5 9 13 17, so B = 2a-1
So when a equals 117, B = 117x2-1 = 233