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 | 0 |
| 4 | 12 |
| 5 | 0 |
| 6 | -120 |
| 7 | 0 |
| 8 | 1680 |
| 9 | 0 |
| 10 | -30240 |
| 11 | 0 |
| 12 | 665280 |
| 13 | 0 |
| 14 | -17297280 |
| 15 | 0 |
| 16 | 518918400 |
| 17 | 0 |
| 18 | -17643225600 |
| 19 | 0 |
| 20 | 670442572800 |
| 21 | 0 |
| 22 | -28158588057600 |
| 23 | 0 |
| 24 | 1295295050649600 |
| 25 | 0 |
| 26 | -64764752532480000 |
| 27 | 0 |
| 28 | 3497296636753920000 |
| 29 | 0 |
| 30 | -202843204931727360000 |
| 31 | 0 |