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 | 0 |
| 2 | -1 |
| 3 | -1 |
| 4 | -1 |
| 5 | 13 |
| 6 | 7951 |
| 7 | 21599 |
| 8 | -294997 |
| 9 | -275833 |
| 10 | -60527057 |
| 11 | -6338125867 |
| 12 | 37620769159 |
| 13 | 10425684579701 |
| 14 | 5113538085001361 |
| 15 | -25594556368763237 |
| 16 | -6013201989263028181 |
| 17 | -3771502911169983097219 |
| 18 | 18335649295377317231411 |
| 19 | 669255665793644548301365603 |