The systematic pythagorean numbers generation.

The function primitive_pythagorean_number is a sysmtematic pythagorean
numbers generator.
a trial to make the process fast but not success

In decimal, the sum of digit numbers means the remainder of the number
divided by 9, for example, the digit numbers of 123 are 1, 2 and 3 the
sum of them is 6, the remainder 123 divided by 9 is 6 since 123 = 9*13
+ 6.
We use the simular principle.