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 | 1 |
| 3 | 720 |
| 4 | 1 |
| 5 | 5040 |
| 6 | 1036800 |
| 7 | 10080 |
| 8 | 3628800 |
| 9 | 24634368000 |
| 10 | 6350400 |
| 11 | 747242496000 |
| 12 | 3476402012160000 |
| 13 | 105670656000 |
| 14 | 11298306539520000 |
| 15 | 1489290622009344000000 |
| 16 | 2259661307904000 |
| 17 | 6688268793387417600000 |
| 18 | 920024174652492349440000000 |
| 19 | 8655406673795481600000 |