!*********************************************************************
!*   This program computes Euler number En using subroutine EULERA   *
!* ----------------------------------------------------------------- *
!* SAMPLE RUN:                                                       *
!*  Compute Euler number En for n = 0,1,...,10.                      *
!*                                                                   *
!*  Please enter Nmax: 10                                            *
!*                                                                   *
!*    n            En                                                *
!*  --------------------------                                       *
!*    0    0.100000000000D+01                                        * 
!*    2   -0.100000000000D+01                                        *
!*    4    0.500000000000D+01                                        *
!*    6   -0.610000000000D+02                                        *
!*    8    0.138500000000D+04                                        *
!*   10   -0.505210000000D+05                                        *
!*  --------------------------                                       *
!*                                                                   *
!* ----------------------------------------------------------------- *
!* REFERENCE: "Fortran Routines for Computation of Special Functions,*
!*             jin.ece.uiuc.edu/routines/routines.html".             *
!*                                                                   *
!*                                 F90 Release By J-P Moreau, Paris. *
!*                                        (www.jpmoreau.fr)          *
!*********************************************************************
    PROGRAM MEULERA

    DOUBLE PRECISION E
    
    DIMENSION E(0:200)
    PRINT *,' '
    
    WRITE(*,10,advance='no'); READ *, N

    
    CALL EULERA(N,E)

    PRINT *,' '
    
    WRITE(*,*)'   n            En'
    
    WRITE(*,*)' --------------------------'
    
    DO K=0,N,2
      
      WRITE(*,20)K,E(K)
    END DO
    PRINT *,' '
    STOP

10  FORMAT('  Please enter Nmax: ')
20  FORMAT(2X,I3,D22.12)
    
    END


    

    SUBROUTINE EULERA(N,EN)

!   ======================================

!     Purpose: Compute Euler number En

!     Input :  n --- Serial number

!     Output:  EN(n) --- En

!   ======================================
    
    IMPLICIT DOUBLE PRECISION (A-H,O-Z)
    
    DIMENSION EN(0:N)
    
    EN(0)=1.0D0
    
    DO M=1,N/2
      
      S=1.0D0
      
      DO K=1,M-1
        
        R=1.0D0
        
        DO J=1,2*K
          
          R=R*(2.0D0*M-2.0D0*K+J)/J
        END DO
        
        S=S+R*EN(2*K)
      END DO
      
      EN(2*M)=-S
    END DO
    
    RETURN
    
    END


!end of file meulera.f90