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 | 2 |
| 3 | -21 |
| 4 | -192 |
| 5 | -1095 |
| 6 | 7200 |
| 7 | 243747 |
| 8 | 3088512 |
| 9 | 1360881 |
| 10 | -874437120 |
| 11 | -21701765349 |
| 12 | -186175604736 |
| 13 | 5870711879721 |
| 14 | 292185085151232 |
| 15 | 5507319584787795 |
| 16 | -38951106749890560 |
| 17 | -6402114772676575263 |
| 18 | -212680600451474522112 |
| 19 | -1602903494245708491957 |
| 20 | 197042528380347210792960 |