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 | 20 |
| 3 | 234 |
| 4 | 2144 |
| 5 | 16750 |
| 6 | 117432 |
| 7 | 761460 |
| 8 | 4654848 |
| 9 | 27173718 |
| 10 | 152867000 |
| 11 | 834212236 |
| 12 | 4438175040 |
| 13 | 23108423884 |
| 14 | 118111709744 |
| 15 | 594059985000 |
| 16 | 2946077521920 |
| 17 | 14429322555750 |
| 18 | 69892354873080 |
| 19 | 335194270938780 |
| 20 | 1593211647720000 |
| 21 | 7511501237722020 |
| 22 | 35153884344493200 |