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 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 60 |
| 6 | 480 |
| 7 | 5250 |
| 8 | 40656 |
| 9 | 363384 |
| 10 | 4839120 |
| 11 | 65198430 |
| 12 | 859543080 |
| 13 | 13311494196 |
| 14 | 233478687624 |
| 15 | 4190929145130 |
| 16 | 79746180437280 |
| 17 | 1667320408619760 |
| 18 | 36965002127643936 |
| 19 | 854734007793179574 |
| 20 | 20962277675893792440 |
| 21 | 544839141515795731500 |