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 | -3 |
| 3 | 3 |
| 4 | 11 |
| 5 | -54 |
| 6 | 66 |
| 7 | 297 |
| 8 | -1575 |
| 9 | 1980 |
| 10 | 10300 |
| 11 | -55392 |
| 12 | 68352 |
| 13 | 403583 |
| 14 | -2153685 |
| 15 | 2551845 |
| 16 | 16999045 |
| 17 | -89142087 |
| 18 | 99986901 |
| 19 | 750955382 |
| 20 | -3850437018 |
| 21 | 4041467331 |
| 22 | 34310059311 |
| 23 | -171533033904 |
| 24 | 166630375248 |
| 25 | 1607168518073 |
| 26 | -7821913867611 |
| 27 | 6950050797297 |