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 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 72 |
| 5 | 570 |
| 6 | 4635 |
| 7 | 39186 |
| 8 | 345828 |
| 9 | 3188268 |
| 10 | 30684150 |
| 11 | 307870365 |
| 12 | 3215425554 |
| 13 | 34899450768 |
| 14 | 393015753039 |
| 15 | 4585024011015 |
| 16 | 55332235452960 |
| 17 | 689799432341928 |
| 18 | 8871905851132041 |
| 19 | 117581467377389310 |
| 20 | 1603990651356920730 |