SUBROUTINE MFFTC6(C,FAC)**   PURPOSE:*       ELEMENTARY GENTLEMAN-SANDE RADIX 5 STEP APPLIED TO A VECTOR-OF*       2-VECTORS-OF-COMPLEX C[IMS,NM [IVS,NV [IES,NE]]].*       SEE REF.[1] FOR NOTATIONS.*       THIS ROUTINE CAN BE USED ONLY BY ROUTINE MFFTDM, WHICH CONTROLS*       ITS OPERATION THROUGH THE MFFTPA COMMON**   DUMMY ARGUMENTS :**   C   ARRAY BEING FOURIER  TRANSFORMED*   FAC PHASE FACTORS, PREPARED BY MFFTP; NOT MODIFIED IN OUTPUT*      COMMON /MFFTPA/  IMS,IVS,IES,NM,NV,NE,MX,LX,MLIM,MSTEP,LLIM,LSTEP,     $ NUSTEP,IVLIM,ILIM,MD2LIM,LD2LIM      INTEGER NUSTEP      COMPLEX C(0:NUSTEP-1,0:4),FAC(0:*)      COMPLEX T1,T2,T3,T4,T5,F1,F2,F3,F4      REAL SIN72,RAD5D4,S36D72      PARAMETER (     $ SIN72 =  9.51056516295153572116439333E-1,     $ RAD5D4 =  5.59016994374947424102293417E-1,     $ S36D72 =  6.18033988749894848204586834E-1 )*..  MU > 0            MUF=LX            DO 200 MU=MSTEP,MLIM,MSTEP              F1=CONJG(FAC(MUF))              F2=CONJG(FAC(MUF*2))              F3=CONJG(FAC(MUF*3))              F4=CONJG(FAC(MUF*4))              DO 190 LAM=MU,MU+LLIM,LSTEP                DO 180 IV=LAM,LAM+IVLIM,IVS                DO 180 I=IV,IV+ILIM,IES                  T1=C(I,1)+C(I,4)                  T2=C(I,2)+C(I,3)                  T3=(C(I,1)-C(I,4))*SIN72                  T4=(C(I,2)-C(I,3))*SIN72                  T5=T1+T2                  T1=RAD5D4*(T1-T2)                  T2=C(I,0)-0.25*T5                  C(I,0)=C(I,0)+T5                  T5=T2+T1                  T2=T2-T1                  T1=T3+S36D72*T4                  T3=S36D72*T3-T4                  C(I,1)=(T5-CMPLX(-AIMAG(T1),REAL(T1)))*F1                  C(I,4)=(T5+CMPLX(-AIMAG(T1),REAL(T1)))*F4                  C(I,2)=(T2-CMPLX(-AIMAG(T3),REAL(T3)))*F2                  C(I,3)=(T2+CMPLX(-AIMAG(T3),REAL(T3)))*F3  180           CONTINUE  190         CONTINUE              MUF=MUF+LX200         CONTINUE            DO 193 LAM=0,LLIM,LSTEP              DO 183 IV=LAM,LAM+IVLIM,IVS              DO 183 I=IV,IV+ILIM,IES                T1=C(I,1)+C(I,4)                T2=C(I,2)+C(I,3)                T3=(C(I,1)-C(I,4))*SIN72                T4=(C(I,2)-C(I,3))*SIN72                T5=T1+T2                T1=RAD5D4*(T1-T2)                T2=C(I,0)-0.25*T5                C(I,0)=C(I,0)+T5                T5=T2+T1                T2=T2-T1                T1=T3+S36D72*T4                T3=S36D72*T3-T4                C(I,1)=T5-CMPLX(-AIMAG(T1),REAL(T1))                C(I,4)=T5+CMPLX(-AIMAG(T1),REAL(T1))                C(I,2)=T2-CMPLX(-AIMAG(T3),REAL(T3))                C(I,3)=T2+CMPLX(-AIMAG(T3),REAL(T3))183           CONTINUE193         CONTINUE      END