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 | 3 |
| 2 | 16 |
| 3 | 75 |
| 4 | 356 |
| 5 | 1770 |
| 6 | 9306 |
| 7 | 51821 |
| 8 | 305232 |
| 9 | 1897227 |
| 10 | 12411650 |
| 11 | 85234864 |
| 12 | 612903324 |
| 13 | 4604004691 |
| 14 | 36050248752 |
| 15 | 293659886235 |
| 16 | 2483993559376 |
| 17 | 21781908622738 |
| 18 | 197701336871190 |
| 19 | 1854695911048053 |
| 20 | 17960309481562600 |
| 21 | 179309794875495795 |