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 | 12 |
| 5 | 120 |
| 6 | 780 |
| 7 | 4212 |
| 8 | 20412 |
| 9 | 93360 |
| 10 | 409260 |
| 11 | 1749780 |
| 12 | 7338000 |
| 13 | 30394560 |
| 14 | 124700928 |
| 15 | 508291692 |
| 16 | 2061586800 |
| 17 | 8332140720 |
| 18 | 33585682920 |
| 19 | 135116412660 |
| 20 | 542785390680 |
| 21 | 2178110585388 |
| 22 | 8733343485120 |