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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | 3 |
| 5 | -5 |
| 6 | -140 |
| 7 | 3265 |
| 8 | -35145 |
| 9 | -423300 |
| 10 | 29156450 |
| 11 | -244674300 |
| 12 | -35711239900 |
| 13 | 1323533263450 |
| 14 | 79091925545150 |
| 15 | -7803803198306500 |
| 16 | -249393437031632750 |
| 17 | 68360119098495114000 |
| 18 | 386044168785212367500 |
| 19 | -899401682046014451577000 |