Question

2, 4, 13, 49, 193, . . .

Which term should be removed so that the sequence follows the rule?

Answer 1

There's something special about the difference of two consecutive terms. But one of those differences doesn't have that same special thing in common. What do you notice about 3 of these numbers?

4 - 2 = 2
13 - 4 = 9
49 - 13 = 36
193 - 49 = 144