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 | -1 |
| 3 | 12 |
| 4 | -16 |
| 5 | 1 |
| 6 | 2160 |
| 7 | -3312 |
| 8 | 381 |
| 9 | -1 |
| 10 | 6048000 |
| 11 | -10137600 |
| 12 | 1603680 |
| 13 | -10496 |
| 14 | 1 |
| 15 | 266716800000 |
| 16 | -476703360000 |
| 17 | 92708406000 |
| 18 | -1022881200 |
| 19 | 307505 |
| 20 | -1 |
| 21 | 186313420339200000 |
| 22 | -349935855575040000 |
| 23 | 78981336366912000 |
| 24 | -1242627237734400 |
| 25 | 750409713900 |
| 26 | -9316560 |
| 27 | 1 |