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 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 112 |
| 5 | 909 |
| 6 | 7833 |
| 7 | 74603 |
| 8 | 740541 |
| 9 | 7656219 |
| 10 | 81187518 |
| 11 | 878435208 |
| 12 | 9647220024 |
| 13 | 107137240686 |
| 14 | 1199914011387 |
| 15 | 13521738420240 |
| 16 | 153051832116378 |
| 17 | 1737562815056865 |
| 18 | 19762347822563532 |
| 19 | 224970273310192579 |
| 20 | 2561375647064514444 |
| 21 | 29149168085832027732 |