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 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 35 |
| 6 | 180 |
| 7 | 910 |
| 8 | 4494 |
| 9 | 22049 |
| 10 | 107580 |
| 11 | 523765 |
| 12 | 2546280 |
| 13 | 12370436 |
| 14 | 60074196 |
| 15 | 291677905 |
| 16 | 1416019290 |
| 17 | 6873991055 |
| 18 | 33368325084 |
| 19 | 161976597634 |
| 20 | 786259649010 |
| 21 | 3816607413905 |
| 22 | 18526261416960 |