Drop str() printers for factorial/subfactorial/etc (issue 3781)
Fix tests for factorial printing (issue 3781)
Fix docstring tests for factorial printing (issue 3781)
Change signs in test for issue 2934
Merge pull request #2047 from skirpichev/3781-factorial-str-print

Drop str() printers for factorial/subfactorial/etc (issue 3781)