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 | 0 |
| 2 | 2 |
| 3 | -3 |
| 4 | 12 |
| 5 | -40 |
| 6 | 190 |
| 7 | -1071 |
| 8 | 7224 |
| 9 | -56232 |
| 10 | 495898 |
| 11 | -4880755 |
| 12 | 53005700 |
| 13 | -629398848 |
| 14 | 8110146070 |
| 15 | -112690225935 |
| 16 | 1679413757168 |
| 17 | -26719024870576 |
| 18 | 451969255722162 |
| 19 | -8099650628337987 |
| 20 | 153288815339260796 |
| 21 | -3054957193416951480 |
| 22 | 63949589015139119598 |
| 23 | -1402819397613793354063 |