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 | 1 |
| 4 | 9 |
| 5 | 41 |
| 6 | 121 |
| 7 | -279 |
| 8 | -1679 |
| 9 | 1009 |
| 10 | 259281 |
| 11 | 1173041 |
| 12 | 669241 |
| 13 | -267141159 |
| 14 | -1295686391 |
| 15 | 10821721 |
| 16 | 650092657761 |
| 17 | 3480768830561 |
| 18 | 17723446561 |
| 19 | -2911516748764191 |
| 20 | -17068971040559639 |
| 21 | 427036022281 |
| 22 | 21673592659354854681 |
| 23 | 137752098937383025481 |