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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 42 |
| 7 | 156 |
| 8 | 570 |
| 9 | 2124 |
| 10 | 7926 |
| 11 | 29844 |
| 12 | 112812 |
| 13 | 428712 |
| 14 | 1635108 |
| 15 | 6259236 |
| 16 | 24031260 |
| 17 | 92517180 |
| 18 | 357019224 |
| 19 | 1380671532 |
| 20 | 5349496152 |
| 21 | 20762603724 |
| 22 | 80709201504 |
| 23 | 314178212928 |
| 24 | 1224576411084 |
| 25 | 4778651920092 |
| 26 | 18667769062044 |