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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 31 |
| 4 | 224 |
| 5 | 1844 |
| 6 | 17028 |
| 7 | 174284 |
| 8 | 1958176 |
| 9 | 23959760 |
| 10 | 317128240 |
| 11 | 4514617360 |
| 12 | 68784608640 |
| 13 | 1116787186240 |
| 14 | 19248968150720 |
| 15 | 351024831699520 |
| 16 | 6752328440253440 |
| 17 | 136640443206206720 |
| 18 | 2901703626188801280 |
| 19 | 64522443639953657600 |