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 | 6 |
| 3 | 18 |
| 4 | 60 |
| 5 | 202 |
| 6 | 718 |
| 7 | 2600 |
| 8 | 9748 |
| 9 | 37270 |
| 10 | 146058 |
| 11 | 582548 |
| 12 | 2367028 |
| 13 | 9761890 |
| 14 | 40844168 |
| 15 | 173001018 |
| 16 | 741193056 |
| 17 | 3207480526 |
| 18 | 14008373662 |
| 19 | 61683982696 |
| 20 | 273658651700 |
| 21 | 1222314257450 |
| 22 | 5493414465900 |
| 23 | 24828463984518 |