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 | 2 |
| 2 | -2 |
| 3 | 14 |
| 4 | -70 |
| 5 | 426 |
| 6 | -2714 |
| 7 | 18118 |
| 8 | -124814 |
| 9 | 881042 |
| 10 | -6339058 |
| 11 | 46318334 |
| 12 | -342769750 |
| 13 | 2563781690 |
| 14 | -19350683018 |
| 15 | 147197511222 |
| 16 | -1127334112542 |
| 17 | 8685458120226 |
| 18 | -67270210217186 |
| 19 | 523472089991662 |
| 20 | -4090668558473318 |
| 21 | 32088204418069450 |
| 22 | -252576222775705466 |