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 | -1 |
| 3 | 5 |
| 4 | 7 |
| 5 | -19 |
| 6 | -869 |
| 7 | 715 |
| 8 | 2339 |
| 9 | -200821 |
| 10 | -12863 |
| 11 | 2117 |
| 12 | 7106149 |
| 13 | -64604977 |
| 14 | -131301607 |
| 15 | 7629931291 |
| 16 | 174053933 |
| 17 | -19449462373 |
| 18 | -46949081169401 |
| 19 | 355455588729389 |
| 20 | 10635113572583999 |
| 21 | -6511303438681407901 |
| 22 | -349640201588122693 |
| 23 | 9112944418860287 |