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 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 66 |
| 6 | 214 |
| 7 | 688 |
| 8 | 2206 |
| 9 | 7070 |
| 10 | 22660 |
| 11 | 72634 |
| 12 | 232830 |
| 13 | 746352 |
| 14 | 2392486 |
| 15 | 7669286 |
| 16 | 24584436 |
| 17 | 78807122 |
| 18 | 252621702 |
| 19 | 809796400 |
| 20 | 2595858574 |