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 | 3 |
| 2 | 12 |
| 3 | 69 |
| 4 | 504 |
| 5 | 4380 |
| 6 | 44280 |
| 7 | 509670 |
| 8 | 6572160 |
| 9 | 93813552 |
| 10 | 1467910080 |
| 11 | 24976440720 |
| 12 | 459045195840 |
| 13 | 9061616266560 |
| 14 | 191187467190720 |
| 15 | 4293103436622000 |
| 16 | 102216550583347200 |
| 17 | 2572022267758944000 |
| 18 | 68195046359419499520 |
| 19 | 1900236334204732043520 |