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 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 8 |
| 6 | 20 |
| 7 | 80 |
| 8 | 210 |
| 9 | 896 |
| 10 | 3360 |
| 11 | 19200 |
| 12 | 79200 |
| 13 | 506880 |
| 14 | 2745600 |
| 15 | 21964800 |
| 16 | 108108000 |
| 17 | 820019200 |
| 18 | 5227622400 |
| 19 | 48881664000 |
| 20 | 319258368000 |
| 21 | 3143467008000 |
| 22 | 25540669440000 |
| 23 | 299677188096000 |
| 24 | 2261626278912000 |
| 25 | 25732281217843200 |
| 26 | 241240136417280000 |