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) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 720 |
| 7 | 2940 |
| 8 | 10080 |
| 9 | 31248 |
| 10 | 90720 |
| 11 | 251460 |
| 12 | 673200 |
| 13 | 1753752 |
| 14 | 4468464 |
| 15 | 11176620 |
| 16 | 27518400 |
| 17 | 66838560 |
| 18 | 160422336 |
| 19 | 381014676 |
| 20 | 896518800 |
| 21 | 2091893160 |
| 22 | 4844402640 |
| 23 | 11142147324 |
| 24 | 25467789600 |
| 25 | 57881367600 |
| 26 | 130862253600 |
| 27 | 294440105700 |
| 28 | 659545876080 |