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 | 600 |
| 7 | 3720 |
| 8 | 27240 |
| 9 | 229080 |
| 10 | 2170680 |
| 11 | 20452440 |
| 12 | 217008600 |
| 13 | 2550317880 |
| 14 | 32808887160 |
| 15 | 457907248920 |
| 16 | 6355848354360 |
| 17 | 95721761831160 |
| 18 | 1551458493435480 |
| 19 | 26890032710452440 |
| 20 | 495810323060597880 |
| 21 | 9097662007250393880 |
| 22 | 177624183228083188440 |