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 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 261 |
| 5 | 1534 |
| 6 | 9319 |
| 7 | 56808 |
| 8 | 353362 |
| 9 | 2227380 |
| 10 | 14099553 |
| 11 | 89931668 |
| 12 | 577292621 |
| 13 | 3718701300 |
| 14 | 24047442913 |
| 15 | 156059054586 |
| 16 | 1015345651345 |
| 17 | 6621929417524 |
| 18 | 43283675452318 |
| 19 | 283439130488986 |
| 20 | 1859169844171611 |