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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 240 |
| 6 | 5040 |
| 7 | 110880 |
| 8 | 2298240 |
| 9 | 47900160 |
| 10 | 1117670400 |
| 11 | 31654022400 |
| 12 | 1064820556800 |
| 13 | 39404587622400 |
| 14 | 1532420002713600 |
| 15 | 62512065487872000 |
| 16 | 2723498636931072000 |
| 17 | 128376129298120704000 |
| 18 | 6524556605528113152000 |
| 19 | 352829667414210674688000 |