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 | 0 |
| 3 | 8 |
| 4 | -16 |
| 5 | -336 |
| 6 | 2464 |
| 7 | 30176 |
| 8 | -572160 |
| 9 | -3654400 |
| 10 | 193852928 |
| 11 | -29664768 |
| 12 | -88869165056 |
| 13 | 788014352384 |
| 14 | 51013392617472 |
| 15 | -1125131950034944 |
| 16 | -33201578814668800 |
| 17 | 1536045242886979584 |
| 18 | 19518336239699623936 |
| 19 | -2267097378027280924672 |