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 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 160 |
| 5 | 1456 |
| 6 | 15904 |
| 7 | 202672 |
| 8 | 2951680 |
| 9 | 48361216 |
| 10 | 880405504 |
| 11 | 17630351872 |
| 12 | 385148108800 |
| 13 | 9114999832576 |
| 14 | 232311251144704 |
| 15 | 6343764407375872 |
| 16 | 184778982658539520 |
| 17 | 5718564661248065536 |
| 18 | 187389427488113557504 |
| 19 | 6481629887083387420672 |
| 20 | 235993351028007334051840 |