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 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 12 |
| 4 | 24 |
| 5 | 80 |
| 6 | 2520 |
| 7 | 17136 |
| 8 | 124320 |
| 9 | 2462400 |
| 10 | 30965760 |
| 11 | 372113280 |
| 12 | 7014807360 |
| 13 | 122840789760 |
| 14 | 2078973921024 |
| 15 | 43236813312000 |
| 16 | 932206147891200 |
| 17 | 20090534745415680 |
| 18 | 480054835899371520 |
| 19 | 12126262777282805760 |
| 20 | 313198020852233932800 |