4x4x4x4x4x4x4 = 16384
This answer is based on assumptions that indicate we want the size of a set S of numbers, the five smallest of which are 1,111,111 1,111,112 1,111,114 1,111,117 1,111,121 and the two largest of which are 7,777,774 7,777,777 The following two numbers would therefore not be in S: 1 777,777 The answer is: 47 = (4x4x4x4x4x4x4) = 16,384
1, 4, 7, 10, 13, ... (Arithmetic sequence, start with 1, add 3 for each successive term);10, 5, 2.5, 1.25, 0.625, ... (Geometric sequence, start with 10, halve for each successive term);2, 3, 5, 7, 11, 13, 17, ... (Prime numbers, no simple rule).