C #FAC2 V1A 15-FEB-72. C LAST UPDATE: C FUNCTION FAC2(N) C C *PURPOSE. C TO RETURN THE REAL FACTORIAL OF HALF THE INTEGER ARGUMENT. C IT IS ASSUMED THAT THE ARGUMENT IS AN EVEN INTEGER. C C *PARAMETERS: C C N - THE EVEN INTEGER VALUE BEING TWICE THE INTEGER WHOSE C FACTORIAL IS RETURNED. C C INPUT PARAMETERS: C N C OUTPUT PARAMETERS: C (FUNCTION VALUE ONLY) C C *METHOD. C CALLS ROUTINE "FCTOR" FROM MRMLIB FOR FACTORIAL. C C *ACCURACY. C C *RESTRICTIONS. C "N" MUST BE EVEN. C C *ERROR CONDITIONS. C C *NON STANDARD ROUTINES CALLED. C FCTOR - FACTORIAL OF INTEGER ARGUMENT - MRMLIB. C C *TYPICAL TIMES. C C *ORIGIN. M.R.MANNING. C C *COMMENTS. C THIS SEEMINGLY USELESS ROUTINE IS IMPLEMENTED FOR THE C BENEFIT OF THE ANGULAR MOMENTUM PACKAGE WHICH USE FACTORIALS C A GREAT DEAL AND HAVE THE STANDARD CONVENTION OF REPRESENTING C PHYSICAL ANGULAR MOMENTUM QUANTUM NUMBERS BY TWICE THEIR VALUE. C THIS ENSURES THAT ALL ANGULAR MOMENTUM QUANTUM NUMBERS ARE C INTEGER BUT MEANS THAT ONE CONTINUALLY REQUIRES FACTORIAL OF C HALF THE ARGUMENT! THIS ROUTINE IS RIPE FOR IMPROVING BY C BEING WRITTEN IN MACHINE LANGUAGE. C C #END. C FAC2=FCTOR(N/2) RETURN END