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 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 12 |
| 5 | 20 |
| 6 | 390 |
| 7 | 2562 |
| 8 | 11816 |
| 9 | 105912 |
| 10 | 1063530 |
| 11 | 8815070 |
| 12 | 81342492 |
| 13 | 895185876 |
| 14 | 9971185406 |
| 15 | 112642410090 |
| 16 | 1372455608400 |
| 17 | 17750397057392 |
| 18 | 236950003516626 |
| 19 | 3286258330135734 |
| 20 | 47688868443593540 |
| 21 | 719345273005797900 |
| 22 | 11222288509573985382 |
| 23 | 181168865439054099266 |