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 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 72 |
| 5 | 480 |
| 6 | 3600 |
| 7 | 30240 |
| 8 | 282240 |
| 9 | 2903040 |
| 10 | 32659200 |
| 11 | 399168000 |
| 12 | 5269017600 |
| 13 | 74724249600 |
| 14 | 1133317785600 |
| 15 | 18307441152000 |
| 16 | 313841848320000 |
| 17 | 5690998849536000 |
| 18 | 108840352997376000 |
| 19 | 2189611807358976000 |
| 20 | 46225138155356160000 |
| 21 | 1021818843434188800000 |