**
**

It can be verified that the sum of the numbers on the diagonals is 101.21 22 23 24 25

20 7 8 9 10

19 6 1 2 11

18 5 4 3 12

17 16 15 14 13

What is the sum of the numbers on the main diagonals in a

**N by N**spiral formed in the same way?

Source: Project Euler