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 | -4 |
| 4 | 4 |
| 5 | 64 |
| 6 | 248 |
| 7 | 48 |
| 8 | -6512 |
| 9 | -51200 |
| 10 | -171296 |
| 11 | 830400 |
| 12 | 17870400 |
| 13 | 144684032 |
| 14 | 441316224 |
| 15 | -5976726784 |
| 16 | -119879356160 |
| 17 | -1123892297728 |
| 18 | -3962230563328 |
| 19 | 70410917051392 |
| 20 | 1686366492509184 |
| 21 | 19578100126072832 |
| 22 | 101728414306826240 |
| 23 | -1258662784047370240 |
| 24 | -42727186269262737408 |