Plotting the table for coefficient of (xn+x52)7 and there cumulative sum :
| Coefficient | Commulative sum |
| x7n→C07 | 1 |
| x6n−5→2×C17 | 1+14 |
| x5n−10→22×C27 | 1+14+84 |
| x4n−15→23×C37 | 1+14+84+280 |
| x3n−20→24×C47 | 1+4+84+280+560=939 |
| x2n−25→25×C57 | |
So,
3n−20≥0∩2n−25<0∩n∈I
∴7≤n≤12
Sum =7+8+9+10+11+12=57