Why do we often only introduce the arithmetic sequence formula post-16?

2. If you only teach one method, which method do you teach and why? Does each method lend itself to another concept in the curriculum?

3. The standard formula for an arithmetic sequence is given in cell 4. However, you can use any term in the formula u_n = u_x + (n – x)d; would you consider teaching this more general form, even though it may not appear in formula booklets?

4. In regards to cell 2, the zeroth term is equivalent to the y-intercept, and the difference is equivalent to the gradient on a co-ordinate grid. How best could you represent or teach this integral connection?