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 | -6 |
| 4 | -12 |
| 5 | 140 |
| 6 | 1020 |
| 7 | -5208 |
| 8 | -117264 |
| 9 | -2448 |
| 10 | 17756640 |
| 11 | 117905040 |
| 12 | -3177424800 |
| 13 | -56997933408 |
| 14 | 523176632160 |
| 15 | 25824592321920 |
| 16 | 31907065317120 |
| 17 | -12118922683971840 |
| 18 | -151839867298498560 |
| 19 | 5619086944920958464 |
| 20 | 172859973799199892480 |
| 21 | -1989399401447725854720 |
| 22 | -170925579909303883614720 |