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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | -2 |
| 6 | 0 |
| 7 | 6 |
| 8 | 0 |
| 9 | -24 |
| 10 | 0 |
| 11 | 120 |
| 12 | 40 |
| 13 | 0 |
| 14 | -720 |
| 15 | -420 |
| 16 | 0 |
| 17 | 5040 |
| 18 | 3948 |
| 19 | 0 |
| 20 | -40320 |
| 21 | -38304 |
| 22 | -2240 |
| 23 | 0 |
| 24 | 362880 |
| 25 | 396576 |
| 26 | 50400 |