C Collection of code snippets by Arne Vajhøj 
C (from articles on eksperten.dk / vajhoej.dk written sometime between 2004 and now) 
      PROGRAM IO
      INTEGER*4 I,N
      INTEGER*4 FAC
      EXTERNAL FAC
      WRITE(6,1000)
      READ(5,1100) N
      DO 100 I=1,N
        WRITE(6,1200) 'I=',I,'FAC(I)=',FAC(I),
     +                'I=',N+I,'FAC(I)=',FAC(N+I)
100   CONTINUE
1000  FORMAT(1X,'Enter max value: ',$)
1100  FORMAT(I2)
1200  FORMAT(1X,2(A2,I2,1X,A7,I8,1X))
      END
C
      INTEGER*4 FUNCTION FAC(N)
      INTEGER*4 N
      INTEGER*4 RES,I
      RES=1
      DO 100 I=1,N
        RES=RES*I
100   CONTINUE
      FAC=RES
      RETURN
      END