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 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | -3 |
| 4 | 9 |
| 5 | -31 |
| 6 | 153 |
| 7 | -1075 |
| 8 | 8689 |
| 9 | -72031 |
| 10 | 605201 |
| 11 | -5282051 |
| 12 | 49239225 |
| 13 | -497094079 |
| 14 | 5410919273 |
| 15 | -62597718643 |
| 16 | 759331611489 |
| 17 | -9586004915007 |
| 18 | 125701843190689 |
| 19 | -1713676634245251 |
| 20 | 24313707650733289 |
| 21 | -358906747784541151 |
| 22 | 5502327502961296825 |
| 23 | -87382907614533531443 |