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 | 1 |
| 3 | 4 |
| 4 | 22 |
| 5 | 152 |
| 6 | 1251 |
| 7 | 11980 |
| 8 | 130908 |
| 9 | 1607488 |
| 10 | 21915525 |
| 11 | 328477396 |
| 12 | 5368649634 |
| 13 | 95026828136 |
| 14 | 1810930007495 |
| 15 | 36968511612124 |
| 16 | 804857864647544 |
| 17 | 18615565047797520 |
| 18 | 455834881650397833 |
| 19 | 11780900281221329892 |