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 | 3 |
| 4 | 8 |
| 5 | -15 |
| 6 | 264 |
| 7 | -35 |
| 8 | -1968 |
| 9 | 87633 |
| 10 | -499600 |
| 11 | 2375901 |
| 12 | 48964200 |
| 13 | -830424023 |
| 14 | 9884072184 |
| 15 | -11730111315 |
| 16 | -1407884197216 |
| 17 | 36601422429345 |
| 18 | -416600839315872 |
| 19 | 191233500832189 |
| 20 | 136472124267672120 |
| 21 | -3513232740127917639 |
| 22 | 46653752740647748520 |