This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 15 |
| 4 | 25 |
| 5 | -25 |
| 6 | -375 |
| 7 | -1625 |
| 8 | -4375 |
| 9 | -5625 |
| 10 | 15625 |
| 11 | 134375 |
| 12 | 515625 |
| 13 | 1234375 |
| 14 | 1015625 |
| 15 | -7265625 |
| 16 | -46484375 |
| 17 | -159765625 |
| 18 | -333984375 |
| 19 | -72265625 |
| 20 | 2978515625 |
| 21 | 15615234375 |
| 22 | 48291015625 |
| 23 | 85302734375 |
| 24 | -56396484375 |
| 25 | -1135009765625 |
| 26 | -5111083984375 |
| 27 | -14205322265625 |