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 | 10 |
| 3 | 68 |
| 4 | 580 |
| 5 | 5912 |
| 6 | 69784 |
| 7 | 933200 |
| 8 | 13912336 |
| 9 | 228390560 |
| 10 | 4088594464 |
| 11 | 79186453568 |
| 12 | 1648396356160 |
| 13 | 36678170613632 |
| 14 | 868239454798720 |
| 15 | 21776352497954048 |
| 16 | 576629116655862016 |
| 17 | 16069766602389885440 |
| 18 | 470015788927133039104 |
| 19 | 14392014594072635786240 |