It does have something to do with that, read this: http://www.ti.com/calc/docs/faq/83faq028.htm >A friend of mine with a TI-83 enters 1.5! (1.5 factorial) and gets a calculated >result. (I can't recall the exact number.) >What is the calculator doing? I initially assumed it was related to the gamma >function but that appears not to be the case.