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 | -8 |
| 5 | 64 |
| 6 | -592 |
| 7 | 6768 |
| 8 | -90624 |
| 9 | 1395840 |
| 10 | -24292608 |
| 11 | 471453696 |
| 12 | -10094066688 |
| 13 | 236340378624 |
| 14 | -6007053852672 |
| 15 | 164713554069504 |
| 16 | -4846361933021184 |
| 17 | 152300800682754048 |
| 18 | -5091189648734748672 |
| 19 | 180386551596145508352 |
| 20 | -6752521487083688165376 |