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 | 42 |
| 4 | 216 |
| 5 | 1320 |
| 6 | 9360 |
| 7 | 75600 |
| 8 | 685440 |
| 9 | 6894720 |
| 10 | 76204800 |
| 11 | 918086400 |
| 12 | 11975040000 |
| 13 | 168129561600 |
| 14 | 2528170444800 |
| 15 | 40537905408000 |
| 16 | 690452066304000 |
| 17 | 12449059983360000 |
| 18 | 236887827111936000 |
| 19 | 4744158915944448000 |
| 20 | 99748982335242240000 |