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) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 132 |
| 4 | 4680 |
| 5 | 214080 |
| 6 | 12416400 |
| 7 | 896132160 |
| 8 | 79295610240 |
| 9 | 8481591336960 |
| 10 | 1081908144172800 |
| 11 | 162548813750400000 |
| 12 | 28443681284170521600 |
| 13 | 5739117489117031219200 |
| 14 | 1323378125974080765388800 |
| 15 | 345972881092262536240128000 |
| 16 | 101817548412839690547916800000 |