Explicit equations for X_1(N) that have been optimized to reduce both the degree and coefficient sizes are available for N <= 50 at [http://math.mit.edu/~drew/X1_curves.txt][1].  These were obtained using the algorithm described in [http://arxiv.org/abs/0811.0296][2].


**EDIT**: Tables of defining equations for X_1(N) for N <= 189 are now available at [http://www-math.mit.edu/~drew/X1_altcurves.html][3]


  [1]: http://math.mit.edu/~drew/X1_curves.txt
  [2]: http://arxiv.org/abs/0811.0296
  [3]: http://www-math.mit.edu/~drew/X1_altcurves.html