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 | 7 |
| 4 | 20 |
| 5 | 58 |
| 6 | 174 |
| 7 | 519 |
| 8 | 1550 |
| 9 | 4634 |
| 10 | 13884 |
| 11 | 41616 |
| 12 | 124824 |
| 13 | 374390 |
| 14 | 1123288 |
| 15 | 3369297 |
| 16 | 10107324 |
| 17 | 30320434 |
| 18 | 90961626 |
| 19 | 272878138 |
| 20 | 818632094 |
| 21 | 2455888346 |
| 22 | 7367661682 |
| 23 | 22102935920 |
| 24 | 66308767426 |
| 25 | 198926187730 |
| 26 | 596778527246 |
| 27 | 1790335274112 |
| 28 | 5371006016314 |