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 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 44 |
| 5 | 312 |
| 6 | 2772 |
| 7 | 30024 |
| 8 | 385688 |
| 9 | 5737232 |
| 10 | 96959396 |
| 11 | 1834244296 |
| 12 | 38390799592 |
| 13 | 880648730416 |
| 14 | 21968596282440 |
| 15 | 592083291341520 |
| 16 | 17144219069647920 |
| 17 | 530774988154571040 |
| 18 | 17495673315094986180 |
| 19 | 611738880367145595720 |
| 20 | 22614424027640541372360 |