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 | 1 |
| 3 | 12 |
| 4 | 100 |
| 5 | 720 |
| 6 | 4816 |
| 7 | 30912 |
| 8 | 193600 |
| 9 | 1194240 |
| 10 | 7296256 |
| 11 | 44301312 |
| 12 | 267904000 |
| 13 | 1615810560 |
| 14 | 9728413696 |
| 15 | 58504691712 |
| 16 | 351565004800 |
| 17 | 2111537479680 |
| 18 | 12677814747136 |
| 19 | 76101248090112 |
| 20 | 456744927232000 |