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 | 0 |
| 3 | 6 |
| 4 | -4 |
| 5 | 300 |
| 6 | -828 |
| 7 | 42224 |
| 8 | -266992 |
| 9 | 11916864 |
| 10 | -132472320 |
| 11 | 5688511488 |
| 12 | -95465876064 |
| 13 | 4138883728512 |
| 14 | -95019458907072 |
| 15 | 4276023328128000 |
| 16 | -125481256750340352 |
| 17 | 5958015717717504000 |
| 18 | -212934915549001078272 |
| 19 | 10767675634298110255104 |