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 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 120 |
| 5 | 840 |
| 6 | 7560 |
| 7 | 83160 |
| 8 | 1081080 |
| 9 | 17297280 |
| 10 | 294053760 |
| 11 | 5587021440 |
| 12 | 128501493120 |
| 13 | 3212537328000 |
| 14 | 93163582512000 |
| 15 | 2888071057872000 |
| 16 | 106858629141264000 |
| 17 | 4381203794791824000 |
| 18 | 188391763176048432000 |
| 19 | 8854412869274276304000 |
| 20 | 433866230594439538896000 |