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 | 10 |
| 3 | 66 |
| 4 | 426 |
| 5 | 2964 |
| 6 | 22818 |
| 7 | 195000 |
| 8 | 1842234 |
| 9 | 19120260 |
| 10 | 216604194 |
| 11 | 2662063728 |
| 12 | 35297775930 |
| 13 | 502460232684 |
| 14 | 7644691295970 |
| 15 | 123824090015544 |
| 16 | 2127644969464698 |
| 17 | 38659776477571860 |
| 18 | 740692592536389474 |
| 19 | 14924674961053224000 |
| 20 | 315523813278300959994 |