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 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 96 |
| 6 | 504 |
| 7 | 3216 |
| 8 | 24024 |
| 9 | 205056 |
| 10 | 1965624 |
| 11 | 20886576 |
| 12 | 243511704 |
| 13 | 3089233056 |
| 14 | 42351635064 |
| 15 | 623815221456 |
| 16 | 9823096307544 |
| 17 | 164655323578176 |
| 18 | 2926840752827064 |
| 19 | 54988308080981616 |
| 20 | 1088680464831056664 |
| 21 | 22653422225916839136 |
| 22 | 494229434646381585144 |
| 23 | 11280809162286897977616 |