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 | 12 |
| 4 | 96 |
| 5 | 480 |
| 6 | 5760 |
| 7 | 40320 |
| 8 | 645120 |
| 9 | 5806080 |
| 10 | 116121600 |
| 11 | 1277337600 |
| 12 | 30656102400 |
| 13 | 398529331200 |
| 14 | 11158821273600 |
| 15 | 167382319104000 |
| 16 | 5356234211328000 |
| 17 | 91055981592576000 |
| 18 | 3278015337332736000 |
| 19 | 62282291409321984000 |
| 20 | 2491291656372879360000 |