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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 24 |
| 5 | 17280 |
| 6 | 207360 |
| 7 | 696729600 |
| 8 | 12541132800 |
| 9 | 115880067072000 |
| 10 | 1366643159020339200000 |
| 11 | 40999294770610176000000 |
| 12 | 1854768736099424576471040000000 |
| 13 | 109950690675973888893203251200000000 |
| 14 | 4617929008390903333514536550400000000 |
| 15 | 420600974084243475616503989010432000000000 |