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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 24 |
| 5 | 240 |
| 6 | 2880 |
| 7 | 46080 |
| 8 | 829440 |
| 9 | 18247680 |
| 10 | 510935040 |
| 11 | 15328051200 |
| 12 | 551809843200 |
| 13 | 22072393728000 |
| 14 | 927040536576000 |
| 15 | 42643864682496000 |
| 16 | 2217480963489792000 |
| 17 | 128613895882407936000 |
| 18 | 7716833752944476160000 |
| 19 | 509311027694335426560000 |