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 | 12 |
| 3 | 84 |
| 4 | 616 |
| 5 | 4832 |
| 6 | 42112 |
| 7 | 410368 |
| 8 | 4316800 |
| 9 | 46899648 |
| 10 | 512004480 |
| 11 | 5554843904 |
| 12 | 59657443584 |
| 13 | 633013100288 |
| 14 | 6639969848320 |
| 15 | 69332566233088 |
| 16 | 733169635126272 |
| 17 | 8068863012833280 |
| 18 | 95049764691595264 |
| 19 | 1213724245095528448 |
| 20 | 16619899465108049920 |
| 21 | 238054738089559379968 |