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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 30 |
| 5 | 140 |
| 6 | 615 |
| 7 | 2562 |
| 8 | 10220 |
| 9 | 39384 |
| 10 | 147645 |
| 11 | 541310 |
| 12 | 1948650 |
| 13 | 6908772 |
| 14 | 24180611 |
| 15 | 83702010 |
| 16 | 286978200 |
| 17 | 975725744 |
| 18 | 3293074233 |
| 19 | 11041484022 |
| 20 | 36804946550 |
| 21 | 122037454140 |
| 22 | 402723598431 |
| 23 | 1323234680306 |
| 24 | 4330586226180 |