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 | -12 |
| 3 | -240 |
| 4 | -5040 |
| 5 | -120960 |
| 6 | -3326400 |
| 7 | -103783680 |
| 8 | -3632428800 |
| 9 | -141145804800 |
| 10 | -6033983155200 |
| 11 | -281585880576000 |
| 12 | -14248245557145600 |
| 13 | -777177030389760000 |
| 14 | -45464856277800960000 |
| 15 | -2839804869044183040000 |
| 16 | -188644180586506444800000 |