Answer or Solution : 1. This is just a simple and interesting puzzle to solve.
2. The clue to this puzzle is this is related to digital electronics and computers more than just mathematics.
3. You could find the solution by just seeing the picture rather than closing the eyes and thinking for the solution.
4. The final and important clue to this puzzle is that think in terms of octal numbers.
5. You are right, these are the implications of octal format of numbers 1, 2, 4 and it continues.
6. The first row shows the octal format of 1, which is 001.
7. The second row shows the octal format of 2, which is 010.
8. The third row shows the octal format of 4, which is 100.
9. Hence the final row shows the octal format 011, which is equivalent to 7.
10. Hence the answer is 7.