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 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | 15 |
| 6 | 45 |
| 7 | 105 |
| 8 | 315 |
| 9 | 1323 |
| 10 | 5355 |
| 11 | 18315 |
| 12 | 63855 |
| 13 | 272415 |
| 14 | 1264263 |
| 15 | 5409495 |
| 16 | 22302735 |
| 17 | 101343375 |
| 18 | 507711375 |
| 19 | 2495918223 |
| 20 | 11798364735 |
| 21 | 58074029055 |
| 22 | 309240315615 |
| 23 | 1670570920095 |
| 24 | 8792390355903 |
| 25 | 46886941456575 |
| 26 | 264381946998975 |
| 27 | 1533013006902975 |
| 28 | 8785301059346175 |
| 29 | 50439885753378303 |