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 | -1 |
| 4 | 0 |
| 5 | 4 |
| 6 | -24 |
| 7 | 104 |
| 8 | -88 |
| 9 | 42 |
| 10 | 536 |
| 11 | -7536 |
| 12 | 32230 |
| 13 | -207052 |
| 14 | 791194 |
| 15 | 3748874 |
| 16 | -15956672 |
| 17 | 224309712 |
| 18 | -757708060 |
| 19 | 5189018388 |
| 20 | -172716308 |
| 21 | -386018261228 |
| 22 | 8480676071664 |
| 23 | -124311732591688 |
| 24 | 323984959211694 |
| 25 | -279035374964954 |
| 26 | -7837135693672568 |