/*  slfeulnm.cpp  by K.Tsuru  */
// function ID 4101 DRADIX
/****************************************************************
SLong class
It provides a n-th Euler's number En by use of combination number.
*****************************************************************/
#ifndef SN_H
#include "sn.h"
#endif

SLong EulerNum(uint N)
{
    if(N < 2) return 1;
    uint j, m;
    SLong sum, f;
    if(N >= f.Radix()/2u) f.SetError(f.OUT_OF_RANGE,"EulerNum", 4101);
    SLong* E = new SLong[N + 1];

    E[0].SetLong(1);
    for(m = 1; m <= N; m++){
          sum.SetZero();    // = 0.0;
          for(j=1; j <= m ; j++){
             f = combL(2*m, 2*j)*E[m-j];
             if(j & 1) sum += f;
             else      sum -= f;
          }
          E[m]=sum;
    }
    delete[] E;
    return sum;
}