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 | 2 |
| 2 | 0 |
| 3 | 2 |
| 4 | 12 |
| 5 | 24 |
| 6 | 28 |
| 7 | 120 |
| 8 | 480 |
| 9 | 1056 |
| 10 | 2304 |
| 11 | 8448 |
| 12 | 27760 |
| 13 | 69600 |
| 14 | 191232 |
| 15 | 643104 |
| 16 | 1978560 |
| 17 | 5470080 |
| 18 | 16353792 |
| 19 | 52557312 |
| 20 | 159694848 |
| 21 | 468853760 |
| 22 | 1444300800 |
| 23 | 4549644288 |
| 24 | 13905927936 |
| 25 | 42219904512 |
| 26 | 131505807360 |
| 27 | 411672307200 |
| 28 | 1270614647808 |
| 29 | 3928681875456 |