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 | 0 |
| 4 | -3 |
| 5 | -9 |
| 6 | 21 |
| 7 | 246 |
| 8 | 1065 |
| 9 | -4283 |
| 10 | -67319 |
| 11 | -397484 |
| 12 | 2315941 |
| 13 | 45914155 |
| 14 | 343743037 |
| 15 | -2623221054 |
| 16 | -62980998639 |
| 17 | -571382718039 |
| 18 | 5391435590545 |
| 19 | 152175023203432 |
| 20 | 1622112809355661 |
| 21 | -18232162910685569 |
| 22 | -591788241447761819 |
| 23 | -7247966654986009490 |