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 | 45 |
| 3 | 249 |
| 4 | 1665 |
| 5 | 11817 |
| 6 | 88725 |
| 7 | 683289 |
| 8 | 5381685 |
| 9 | 43046889 |
| 10 | 348684381 |
| 11 | 2852823609 |
| 12 | 23535840225 |
| 13 | 195528140649 |
| 14 | 1634056945605 |
| 15 | 13726075481049 |
| 16 | 115813764494505 |
| 17 | 981010688215689 |
| 18 | 8338590871415805 |
| 19 | 71097458824894329 |
| 20 | 607883273127192897 |