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 | 1 |
| 3 | 3 |
| 4 | 21 |
| 5 | 120 |
| 6 | 300 |
| 7 | 2080 |
| 8 | 11781 |
| 9 | 29403 |
| 10 | 203841 |
| 11 | 1154440 |
| 12 | 2881200 |
| 13 | 19974360 |
| 14 | 113123361 |
| 15 | 282328203 |
| 16 | 1957283461 |
| 17 | 11084934960 |
| 18 | 27665282700 |
| 19 | 191793804840 |
| 20 | 1086210502741 |
| 21 | 2710915376403 |
| 22 | 18793835590881 |
| 23 | 106437544333680 |
| 24 | 265642041604800 |
| 25 | 1841604094101520 |