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 | 1 |
| 3 | -4 |
| 4 | 24 |
| 5 | -157 |
| 6 | 1176 |
| 7 | -9853 |
| 8 | 91498 |
| 9 | -933451 |
| 10 | 10386908 |
| 11 | -125292129 |
| 12 | 1629597910 |
| 13 | -22746009423 |
| 14 | 339288465552 |
| 15 | -5388025686685 |
| 16 | 90782990910394 |
| 17 | -1617895300046011 |
| 18 | 30412104692215604 |
| 19 | -601422325704360009 |
| 20 | 12483373271662252222 |
| 21 | -271375594220745999111 |