Insert the missing number.
7, 26, 63, 124, 215, 342, (....)
Choose the correct choice
A) 222
B) 737
C) 388
D) 511
E) 200
Numbers are (23 - 1), (33 - 1), (43 - 1), (53 - 1), (63 - 1), (73 - 1) etc.   So, the next number is (83 - 1) = (512 - 1)= 
<gadget id="calculator">(512 - 1)</gadget>
<output>511</output>
511.   Answer:511
<result>D</result>
Insert the missing number.
7, 26, 63, 124, 215, 342, (....)