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) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 64 |
| 7 | 204 |
| 8 | 656 |
| 9 | 2120 |
| 10 | 6873 |
| 11 | 22350 |
| 12 | 72881 |
| 13 | 238232 |
| 14 | 780384 |
| 15 | 2561164 |
| 16 | 8419766 |
| 17 | 27721784 |
| 18 | 91397927 |
| 19 | 301710074 |
| 20 | 997087170 |
| 21 | 3298556716 |
| 22 | 10922576840 |
| 23 | 36199599880 |
| 24 | 120068987717 |
| 25 | 398547827336 |
| 26 | 1323821438203 |
| 27 | 4400043488826 |
| 28 | 14633372199291 |