Because I don't know how to calculate the interval point of 13, anyway 15 refers to the vector length of 15. You can modify this value yourself as needed.

The second method is incremental method.

a = 0:pi/ 14:pi

The last number in the vector will be pi/ 14 higher than the previous number. According to the above writing, the vector length is also 15. Pi/ 14 is also modified according to your specific needs.