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 | 4 |
| 2 | 72 |
| 3 | 2000 |
| 4 | 68600 |
| 5 | 2667168 |
| 6 | 112698432 |
| 7 | 5053029696 |
| 8 | 236860767000 |
| 9 | 11493303192800 |
| 10 | 573327757086656 |
| 11 | 29253930349198464 |
| 12 | 1521079361361956032 |
| 13 | 80361335659444000000 |
| 14 | 4304087536829486400000 |
| 15 | 233271979857187430688000 |
| 16 | 12774642558686527109607000 |
| 17 | 706008965215713532853436000 |
| 18 | 39337406606398593529683000000 |