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 | 1 |
| 3 | 16 |
| 4 | 1 |
| 5 | 8 |
| 6 | 3721 |
| 7 | 108 |
| 8 | 10816 |
| 9 | 6568440 |
| 10 | 72900 |
| 11 | 31449600 |
| 12 | 34117784100 |
| 13 | 165564000 |
| 14 | 210350649600 |
| 15 | 402994899820800 |
| 16 | 965895840000 |
| 17 | 2867571383040000 |
| 18 | 9255560083943040000 |
| 19 | 12074509581120000 |
| 20 | 72211625896757760000 |
| 21 | 373919369489319044160000 |
| 22 | 286361814021766560000 |
| 23 | 3107808843778161008640000 |