bridge/class-master/depend/pari/src/basemath/mftrace.c
/* number of elliptic points of order 2 in X0(N) */
number of elliptic points of order 2 in X0(N)
number of elliptic points of order 2 in X0 ( N )
static long
nu2(long N)
{
  long i, l;
  GEN P;
  if ((N&3L) == 0) return 0;
  if (!odd(N)) N >>= 1;
  P = gel(myfactoru(N), 1); l = lg(P);
  for (i = 1; i < l; i++) if ((P[i]&3L) == 3) return 0;
  return 1L<<(l-1);
}
static long nu2 ( long N ) { long i , l ; GEN P ; if ( ( N & 3L ) == 0 ) return 0 ; if ( ! odd ( N ) ) N >>= 1 ; P = gel ( myfactoru ( N ) , 1 ) ; l = lg ( P ) ; for ( i = 1 ; i < l ; i ++ ) if ( ( P [ i ] & 3L ) == 3 ) return 0 ; return 1L << ( l - 1 ) ; }
number of elliptic points of order 2 in X0(N)
number of elliptic points of order 2 in X0 ( N )