code: function x_to_y2 (t, y2, x) {
          sqr(t, x);
          mul_small(y2, x, 486662);
          add(t, t, y2);
          add(t, t, C1);
          mul(y2, t, x);
      }
docs: /* Y^2 = X^3 + 486662 X^2 + X
  t is a temporary