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 | 12 |
| 2 | -72 |
| 3 | 864 |
| 4 | -12960 |
| 5 | 217728 |
| 6 | -3919104 |
| 7 | 73903104 |
| 8 | -1441110528 |
| 9 | 28822210560 |
| 10 | -587973095424 |
| 11 | 12187078705152 |
| 12 | -255928652808192 |
| 13 | 5433562167312384 |
| 14 | -116433475013836800 |
| 15 | 2514963060298874880 |
| 16 | -54700446561500528640 |
| 17 | 1196974477698717450240 |
| 18 | -26333438509371783905280 |
| 19 | 582107588101902591590400 |