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 | -20 |
| 2 | 220 |
| 3 | -1760 |
| 4 | 11420 |
| 5 | -63624 |
| 6 | 315040 |
| 7 | -1418560 |
| 8 | 5903260 |
| 9 | -22976820 |
| 10 | 84413912 |
| 11 | -294841120 |
| 12 | 984745120 |
| 13 | -3159938760 |
| 14 | 9780562880 |
| 15 | -29296914112 |
| 16 | 85169213340 |
| 17 | -240882506920 |
| 18 | 664216884540 |
| 19 | -1788966694240 |
| 20 | 4714033526616 |
| 21 | -12170584419840 |
| 22 | 30826269009760 |