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 | 4 |
| 3 | 24 |
| 4 | 192 |
| 5 | 1920 |
| 6 | 23040 |
| 7 | 322560 |
| 8 | 5160960 |
| 9 | 92897280 |
| 10 | 1857945600 |
| 11 | 40874803200 |
| 12 | 980995276800 |
| 13 | 25505877196800 |
| 14 | 714164561510400 |
| 15 | 21424936845312000 |
| 16 | 685597979049984000 |
| 17 | 23310331287699456000 |
| 18 | 839171926357180416000 |
| 19 | 31888533201572855808000 |
| 20 | 1275541328062914232320000 |