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 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 8 |
| 5 | 20 |
| 6 | 45 |
| 7 | 144 |
| 8 | 448 |
| 9 | 1680 |
| 10 | 4725 |
| 11 | 17280 |
| 12 | 62208 |
| 13 | 290304 |
| 14 | 1254400 |
| 15 | 4465125 |
| 16 | 18144000 |
| 17 | 72990720 |
| 18 | 391910400 |
| 19 | 1881169920 |
| 20 | 9754214400 |
| 21 | 45660160000 |
| 22 | 205752960000 |
| 23 | 905748480000 |
| 24 | 5280992640000 |
| 25 | 28326238617600 |
| 26 | 162956344320000 |
| 27 | 853298675712000 |
| 28 | 5309413982208000 |