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 | 11 |
| 3 | -39 |
| 4 | 633 |
| 5 | -4065 |
| 6 | 86355 |
| 7 | -818055 |
| 8 | 21370545 |
| 9 | -270059265 |
| 10 | 8348125275 |
| 11 | -132575387175 |
| 12 | 4724044288425 |
| 13 | -90632895177825 |
| 14 | 3652562288650275 |
| 15 | -82321915303002375 |
| 16 | 3698358581066774625 |
| 17 | -95898903720429434625 |
| 18 | 4748433998702431912875 |
| 19 | -139390494822185358126375 |