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 | 0 |
| 3 | 2 |
| 4 | -2 |
| 5 | -6 |
| 6 | 16 |
| 7 | 20 |
| 8 | -132 |
| 9 | -28 |
| 10 | 1216 |
| 11 | -936 |
| 12 | -12440 |
| 13 | 23672 |
| 14 | 138048 |
| 15 | -469456 |
| 16 | -1601264 |
| 17 | 9112560 |
| 18 | 18108928 |
| 19 | -182135008 |
| 20 | -161934624 |
| 21 | 3804634784 |
| 22 | -404007680 |
| 23 | -83297957568 |
| 24 | 92590134208 |
| 25 | 1906560847424 |
| 26 | -4221314202624 |
| 27 | -45349267830400 |
| 28 | 159324751301248 |