There is symmetry in the list of differences of cubes........both the diff of squares and the diff of cubes have 19......................19 and 91.....symmetry................217 and 271...............symmetry..........169 is 13 squared..........the list ends with 331....................13 backwards in the last number...........

7	.
19	.
37	.
61	.
91
127	.
169
217	.
271	.
331	.