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 | 1 |
| 4 | 7 |
| 5 | 21 |
| 6 | 126 |
| 7 | 638 |
| 8 | 4264 |
| 9 | 28983 |
| 10 | 226018 |
| 11 | 1872300 |
| 12 | 16940661 |
| 13 | 163461455 |
| 14 | 1688378030 |
| 15 | 18501971647 |
| 16 | 214749109038 |
| 17 | 2628228896227 |
| 18 | 33832314246857 |
| 19 | 456730760934125 |
| 20 | 6451399211318995 |
| 21 | 95135434800384144 |
| 22 | 1461771954435844296 |
| 23 | 23360315241127222572 |