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 | 6 |
| 4 | 8 |
| 5 | 170 |
| 6 | 1872 |
| 7 | 29246 |
| 8 | 519808 |
| 9 | 10698642 |
| 10 | 248787200 |
| 11 | 6458737142 |
| 12 | 185138721792 |
| 13 | 5808233422394 |
| 14 | 197952647108608 |
| 15 | 7283047491096750 |
| 16 | 287705410381709312 |
| 17 | 12145740050403520034 |
| 18 | 545696709922799419392 |
| 19 | 25998534614835587104742 |
| 20 | 1309210567403228200960000 |