From: SourceForge.net <noreply@so...>  20041230 07:05:09

Bugs item #1093138, was opened at 20041230 00:05 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1093138&group_id=4933 Category: Lisp Core Group: None Status: Open Resolution: None Priority: 3 Submitted By: Robert Dodier (robert_dodier) Assigned to: Nobody/Anonymous (nobody) Summary: double factorial defn incorrect for noninteger operand Initial Comment: The double factorial x!! yields an incorrect result for x other than an integer. It appears that x!! is computed as the product x*(x2)*(x4)*...*y, where y is the least term (x2*k) s.t. x2*k > 1. This agrees with published defns (Arfken, Mathworld) for positive integers but not otherwise. Mathworld (http://mathworld.wolfram.com/DoubleFactorial.html) states a formula for z!!, z complex, translated into Maxima as follows  doublefact (z) := block ([a: 1+2*zcos(%pi*z), b: cos(%pi*z)1], 2^(a/4) * %pi^(b/4) * gamma(1+z/2)); It seems that Maxima could evaluate this function for noninteger arguments. Note that Maxima translates input x!! into an noun form genfact (x, x/2, 2).  You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1093138&group_id=4933 