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 | 0 |
| 2 | -1 |
| 3 | 1 |
| 4 | 2 |
| 5 | -9 |
| 6 | 9 |
| 7 | 50 |
| 8 | -267 |
| 9 | 413 |
| 10 | 2180 |
| 11 | -17731 |
| 12 | 50533 |
| 13 | 110176 |
| 14 | -1966797 |
| 15 | 9938669 |
| 16 | -8638718 |
| 17 | -278475061 |
| 18 | 2540956509 |
| 19 | -9816860358 |
| 20 | -27172288399 |
| 21 | 725503033401 |
| 22 | -5592543175252 |
| 23 | 15823587507881 |
| 24 | 168392610536153 |
| 25 | -2848115497132448 |
| 26 | 20819319685262839 |