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 | 9 |
| 2 | 63 |
| 3 | 354 |
| 4 | 1764 |
| 5 | 7947 |
| 6 | 33294 |
| 7 | 131049 |
| 8 | 490437 |
| 9 | 1756243 |
| 10 | 6055749 |
| 11 | 20190402 |
| 12 | 65342031 |
| 13 | 205853535 |
| 14 | 632948256 |
| 15 | 1903369146 |
| 16 | 5608257129 |
| 17 | 16216492509 |
| 18 | 46080035361 |
| 19 | 128829484620 |
| 20 | 354757096107 |
| 21 | 963099596421 |