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 | 1 |
| 2 | 2 |
| 3 | -6 |
| 4 | -4 |
| 5 | -25 |
| 6 | -24 |
| 7 | -42 |
| 8 | 336 |
| 9 | 216 |
| 10 | 2500 |
| 11 | 2376 |
| 12 | 4032 |
| 13 | -52416 |
| 14 | -33264 |
| 15 | -562500 |
| 16 | -532224 |
| 17 | -891072 |
| 18 | 16039296 |
| 19 | 10112256 |
| 20 | 225000000 |
| 21 | 212357376 |
| 22 | 352864512 |
| 23 | -8115883776 |
| 24 | -5096577024 |
| 25 | -140625000000 |
| 26 | -132511002624 |
| 27 | -219128861952 |
| 28 | 6135608134656 |
| 29 | 3842819076096 |
| 30 | 126562500000000 |