Alexander Molnar b7e6591a6c Added content to factorial stub (#34330) ...

* Added content to stub

Added definition, examples and some uses as well as computational info and interesting formulas that occur.

* Update index.md

2019-03-12 01:04:42 +05:30

..

index.md

Added content to factorial stub (#34330)

2019-03-12 01:04:42 +05:30