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 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | -5 |
| 6 | 15 |
| 7 | -35 |
| 8 | 105 |
| 9 | -756 |
| 10 | 6510 |
| 11 | -46530 |
| 12 | 283470 |
| 13 | -1667380 |
| 14 | 11457446 |
| 15 | -99776040 |
| 16 | 969295145 |
| 17 | -9298091180 |
| 18 | 86154691680 |
| 19 | -804769174536 |
| 20 | 8052676029420 |
| 21 | -88489327173660 |
| 22 | 1038440150703340 |
| 23 | -12501684521410700 |
| 24 | 151866259113256611 |