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 | -2 |
| 3 | -6 |
| 4 | -14 |
| 5 | 0 |
| 6 | 278 |
| 7 | 2520 |
| 8 | 15016 |
| 9 | 0 |
| 10 | -2172632 |
| 11 | -53222400 |
| 12 | -835765304 |
| 13 | 0 |
| 14 | 851104689248 |
| 15 | 55249242048000 |
| 16 | 2288258540319136 |
| 17 | 0 |
| 18 | -16212819419809777952 |
| 19 | -2773508758631170560000 |
| 20 | -302332135138133434911104 |
| 21 | 0 |
| 22 | 14824259801049378686209605248 |