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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 24 |
| 5 | 150 |
| 6 | 720 |
| 7 | 1560 |
| 8 | 87360 |
| 9 | 1670760 |
| 10 | 20420400 |
| 11 | 1999157160 |
| 12 | 13085392320 |
| 13 | 3302971111440 |
| 14 | 103154328557280 |
| 15 | 1348374437570160 |
| 16 | 67598505136850688 |
| 17 | 114701988497522458032 |
| 18 | 2307534121538392979232 |
| 19 | 10183789060049355548733936 |