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 | 3 |
| 2 | 12 |
| 3 | 45 |
| 4 | 0 |
| 5 | -3465 |
| 6 | -60480 |
| 7 | -626535 |
| 8 | 0 |
| 9 | 204417675 |
| 10 | 6227020800 |
| 11 | 104928949125 |
| 12 | 0 |
| 13 | -77849405258625 |
| 14 | -3379030566912000 |
| 15 | -78792721832199375 |
| 16 | 0 |
| 17 | 104312208642352585875 |
| 18 | 5875458349746585600000 |
| 19 | 174954117301479619228125 |
| 20 | 0 |
| 21 | -362526128354588965187045625 |
| 22 | -25100240092118201519308800000 |