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 | -9 |
| 3 | -31 |
| 4 | -23 |
| 5 | 3399 |
| 6 | 41311 |
| 7 | 473129 |
| 8 | 1284081 |
| 9 | -79051537 |
| 10 | -2447228249 |
| 11 | -52444297071 |
| 12 | -712806368999 |
| 13 | -2221410364681 |
| 14 | 331443685309647 |
| 15 | 15068893004257049 |
| 16 | 460836352976093281 |
| 17 | 10298306504802529119 |
| 18 | 122928784866003823831 |
| 19 | -3359583359629857247807 |