see meta bug 70798.
Winfried Donkers committed a patch related to this issue.
It has been pushed to "master":
fdo#71936 Add Excel 2010 functions GAMMA.DIST, GAMMA.INV, GAMMALN.PRECISE
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.