1 3 5 7
3 7 15 27
5 15 37 79
7 27 79 x
Let's see how that was built:
Start with the first four odd numbers 1,3,5,7 going
across and down, like this:
1 3 5 7
3
5
7
Now we complete a 2x2 square by adding 3 corners of
the square and putting the sum in the lower right corner
of the square, like this: 1+3+3=7
1 3 5 7
3 7
5
7
Now 3+5+7=15
1 3 5 7
3 7 15
5
7
Now 3+7+5=15
1 3 5 7
3 7 15
5 15
7
Now 5+7+15=27
1 3 5 7
3 7 15 27
5 15
7
Now 5+15+7=27
1 3 5 7
3 7 15 27
5 15
7 27
Now 7+15+15=37
1 3 5 7
3 7 15 27
5 15 37
7 27
Now 15+27+37=79
1 3 5 7
3 7 15 27
5 15 37 79
7 27
Now 15+37+27=79
1 3 5 7
3 7 15 27
5 15 37 79
7 27 79
Now what? You finish :)
Edwin