7, 26, 63, 124, 215, 342, ?

Explanation:-

The terms are given in a series
(2³ -1) = 7
(3³ -1) = 26
(4³ -1) = 63
(5³ -1) = 124
(6³ -1) = 215
(7³ -1) = 342
So, the missing term is,
(8³ -1) = 511.