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 | 4985 |
| 8 | 39440 |
| 9 | 351000 |
| 10 | 3470400 |
| 11 | 37738800 |
| 12 | 447766925 |
| 13 | 5755249449 |
| 14 | 79663786022 |
| 15 | 1181466923370 |
| 16 | 18690124534560 |
| 17 | 314145239141775 |
| 18 | 5590784473674106 |
| 19 | 105025821614503735 |
| 20 | 2076805450110696320 |
| 21 | 43120601826854807940 |
| 22 | 937944680532722764045 |