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 | 3 |
| 4 | 4 |
| 5 | 20 |
| 6 | 36 |
| 7 | 252 |
| 8 | 576 |
| 9 | 5184 |
| 10 | 14400 |
| 11 | 158400 |
| 12 | 518400 |
| 13 | 6739200 |
| 14 | 25401600 |
| 15 | 381024000 |
| 16 | 1625702400 |
| 17 | 27636940800 |
| 18 | 131681894400 |
| 19 | 2501955993600 |
| 20 | 13168189440000 |
| 21 | 276531978240000 |
| 22 | 1593350922240000 |
| 23 | 36647071211520000 |
| 24 | 229442532802560000 |
| 25 | 5736063320064000000 |