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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 0 |
| 6 | 0 |
| 7 | 2520 |
| 8 | 40320 |
| 9 | 0 |
| 10 | 604800 |
| 11 | 39916800 |
| 12 | 479001600 |
| 13 | 259459200 |
| 14 | 50854003200 |
| 15 | 1961511552000 |
| 16 | 21097146470400 |
| 17 | 88921857024000 |
| 18 | 8002967132160000 |
| 19 | 243459152346009600 |
| 20 | 2642401903325184000 |
| 21 | 38318206628782080000 |
| 22 | 2435557926202232832000 |