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) |
|---|---|
| 2 | 1 |
| 3 | -3 |
| 4 | 12 |
| 5 | -70 |
| 6 | 585 |
| 7 | -6741 |
| 8 | 103068 |
| 9 | -2023092 |
| 10 | 49615695 |
| 11 | -1487006785 |
| 12 | 53477384268 |
| 13 | -2272859942574 |
| 14 | 112699083156751 |
| 15 | -6447858833644515 |
| 16 | 421601806346674320 |
| 17 | -31242589674606301224 |
| 18 | 2604618355967848204587 |
| 19 | -242686626407684239621113 |
| 20 | 25124942798118355122058980 |