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 | 1 |
| 4 | 4 |
| 5 | 0 |
| 6 | 10 |
| 7 | 140 |
| 8 | 560 |
| 9 | 280 |
| 10 | 8400 |
| 11 | 92400 |
| 12 | 385000 |
| 13 | 800800 |
| 14 | 16816800 |
| 15 | 169569400 |
| 16 | 784784000 |
| 17 | 3811808000 |
| 18 | 68803134400 |
| 19 | 673546473600 |
| 20 | 3693641952000 |
| 21 | 30454440016000 |
| 22 | 507477434464000 |
| 23 | 5002277568288000 |
| 24 | 33870732912016000 |
| 25 | 386622918281600000 |