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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | 3 |
| 5 | -13 |
| 6 | 69 |
| 7 | -419 |
| 8 | 2809 |
| 9 | -20353 |
| 10 | 157199 |
| 11 | -1281993 |
| 12 | 10963825 |
| 13 | -97828031 |
| 14 | 907177801 |
| 15 | -8716049417 |
| 16 | 86553001779 |
| 17 | -886573220093 |
| 18 | 9351927111901 |
| 19 | -101447092428243 |
| 20 | 1130357986741545 |
| 21 | -12923637003161409 |
| 22 | 151479552582252239 |
| 23 | -1818756036793636033 |