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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 26 |
| 5 | 99 |
| 6 | 352 |
| 7 | 1200 |
| 8 | 3977 |
| 9 | 12918 |
| 10 | 41338 |
| 11 | 130779 |
| 12 | 410048 |
| 13 | 1276512 |
| 14 | 3950929 |
| 15 | 12170598 |
| 16 | 37343834 |
| 17 | 114209811 |
| 18 | 348332320 |
| 19 | 1059927312 |
| 20 | 3218870105 |
| 21 | 9758944470 |
| 22 | 29544747706 |
| 23 | 89335651851 |
| 24 | 269843267456 |
| 25 | 814337329344 |
| 26 | 2455598257057 |
| 27 | 7399746051270 |