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 | 10 |
| 3 | 48 |
| 4 | 312 |
| 5 | 2520 |
| 6 | 24480 |
| 7 | 277200 |
| 8 | 3588480 |
| 9 | 52254720 |
| 10 | 845510400 |
| 11 | 15048633600 |
| 12 | 292190976000 |
| 13 | 6146069529600 |
| 14 | 139223731046400 |
| 15 | 3379030566912000 |
| 16 | 87478184521728000 |
| 17 | 2406225451069440000 |
| 18 | 70080382582898688000 |