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 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 28 |
| 5 | 199 |
| 6 | 1721 |
| 7 | 17394 |
| 8 | 200803 |
| 9 | 2607301 |
| 10 | 37614922 |
| 11 | 596933193 |
| 12 | 10334308029 |
| 13 | 193820343248 |
| 14 | 3914731286181 |
| 15 | 84716451763961 |
| 16 | 1955520075368116 |
| 17 | 47960724925499219 |
| 18 | 1245468599978831333 |
| 19 | 34139796082603477690 |
| 20 | 985066290112167474255 |
| 21 | 29844155285575945561913 |