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 | 4 |
| 3 | 16 |
| 4 | 103 |
| 5 | 711 |
| 6 | 5526 |
| 7 | 48066 |
| 8 | 463248 |
| 9 | 4908816 |
| 10 | 56749536 |
| 11 | 711299232 |
| 12 | 9609618816 |
| 13 | 139252708224 |
| 14 | 2154724104960 |
| 15 | 35464952597760 |
| 16 | 618712803717120 |
| 17 | 11405648080834560 |
| 18 | 221541001069731840 |
| 19 | 4522678391979417600 |
| 20 | 96811891510299033600 |
| 21 | 2168416142767145779200 |