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 | 6 |
| 5 | 30 |
| 6 | 180 |
| 7 | 840 |
| 8 | 5460 |
| 9 | 30996 |
| 10 | 209160 |
| 11 | 1290960 |
| 12 | 9753480 |
| 13 | 69618120 |
| 14 | 571627056 |
| 15 | 4443697440 |
| 16 | 40027718640 |
| 17 | 346953934320 |
| 18 | 3369416698080 |
| 19 | 31421601510336 |
| 20 | 328430320909920 |
| 21 | 3331475969159520 |
| 22 | 37124416523261760 |