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) |
|---|---|
| 3 | 1 |
| 4 | 1 |
| 5 | 5 |
| 6 | 17 |
| 7 | 57 |
| 8 | 189 |
| 9 | 613 |
| 10 | 1949 |
| 11 | 6097 |
| 12 | 18825 |
| 13 | 57525 |
| 14 | 174353 |
| 15 | 525049 |
| 16 | 1573077 |
| 17 | 4693909 |
| 18 | 13960805 |
| 19 | 41415089 |
| 20 | 122603341 |
| 21 | 362343053 |
| 22 | 1069436317 |
| 23 | 3152995209 |
| 24 | 9287942097 |
| 25 | 27341397469 |
| 26 | 80443393889 |
| 27 | 236581555233 |
| 28 | 695561538977 |