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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | 4 |
| 5 | -38 |
| 6 | -78 |
| 7 | 5246 |
| 8 | -11680 |
| 9 | -2066056 |
| 10 | 22308440 |
| 11 | 1898577048 |
| 12 | -48769559680 |
| 13 | -3518093351728 |
| 14 | 174500124820560 |
| 15 | 11809059761527536 |
| 16 | -1021558531563834368 |
| 17 | -66133927485154902144 |
| 18 | 9433326815405995274624 |
| 19 | 578173001867228425792384 |