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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5039 |
| 8 | 40270 |
| 9 | 361302 |
| 10 | 3587916 |
| 11 | 38957991 |
| 12 | 457647966 |
| 13 | 5763075506 |
| 14 | 77182248916 |
| 15 | 1091842643475 |
| 16 | 16219884281650 |
| 17 | 251774983140578 |
| 18 | 4066273930979460 |
| 19 | 68077194367392864 |
| 20 | 1177729684507324152 |
| 21 | 20995515989327134152 |
| 22 | 384762410996641402384 |