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 | 2 |
| 3 | 4 |
| 4 | 8 |
| 5 | 24 |
| 6 | 128 |
| 7 | 624 |
| 8 | 1920 |
| 9 | 8448 |
| 10 | 137472 |
| 11 | 1203456 |
| 12 | 835584 |
| 13 | -23073792 |
| 14 | 1024616448 |
| 15 | 15237156864 |
| 16 | -88263327744 |
| 17 | -2230875095040 |
| 18 | 37715465207808 |
| 19 | 842231374479360 |
| 20 | -10018210447097856 |
| 21 | -278334129792614400 |
| 22 | 4502327717477744640 |
| 23 | 131853718231347363840 |