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 | 0 |
| 1 | 2 |
| 2 | 10 |
| 3 | 48 |
| 4 | 208 |
| 5 | 864 |
| 6 | 3472 |
| 7 | 13640 |
| 8 | 52664 |
| 9 | 200616 |
| 10 | 755992 |
| 11 | 2823688 |
| 12 | 10468856 |
| 13 | 38570504 |
| 14 | 141341944 |
| 15 | 515532424 |
| 16 | 1872673144 |
| 17 | 6777925768 |
| 18 | 24453094264 |
| 19 | 87966879368 |
| 20 | 315629269368 |
| 21 | 1129834372744 |
| 22 | 4035747287416 |
| 23 | 14387491636872 |