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 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 9 |
| 7 | 22 |
| 8 | 69 |
| 9 | 190 |
| 10 | 567 |
| 11 | 1640 |
| 12 | 5025 |
| 13 | 15404 |
| 14 | 49048 |
| 15 | 159074 |
| 16 | 531165 |
| 17 | 1813627 |
| 18 | 6352739 |
| 19 | 22759620 |
| 20 | 83443086 |
| 21 | 312612543 |
| 22 | 1196356133 |
| 23 | 4672620842 |
| 24 | 18615188819 |
| 25 | 75593464871 |
| 26 | 312729620542 |
| 27 | 1317267618429 |
| 28 | 5646454341658 |
| 29 | 24618309943464 |
| 30 | 109123789229297 |