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 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 3 |
| 5 | 10 |
| 6 | 60 |
| 7 | 210 |
| 8 | 700 |
| 9 | 3556 |
| 10 | 19845 |
| 11 | 105567 |
| 12 | 550935 |
| 13 | 3120832 |
| 14 | 19432413 |
| 15 | 127949250 |
| 16 | 858963105 |
| 17 | 5882733142 |
| 18 | 41636699676 |
| 19 | 307105857344 |
| 20 | 2357523511200 |
| 21 | 18694832699907 |
| 22 | 152228641035471 |
| 23 | 1270386473853510 |
| 24 | 10872532998387918 |
| 25 | 95531590347525151 |