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 | -4 |
| 3 | 32 |
| 4 | -240 |
| 5 | 1792 |
| 6 | -11840 |
| 7 | 26112 |
| 8 | 1589504 |
| 9 | -57548800 |
| 10 | 1556757504 |
| 11 | -39250780160 |
| 12 | 973563695104 |
| 13 | -24122607992832 |
| 14 | 596246557736960 |
| 15 | -14477682566889472 |
| 16 | 332039052050104320 |
| 17 | -6425352382711857152 |
| 18 | 53086817854485692416 |
| 19 | 4505005802471597015040 |
| 20 | -419037805969718712991744 |