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 | 0 |
| 1 | 1 |
| 2 | -2 |
| 3 | 1 |
| 4 | -12 |
| 5 | 25 |
| 6 | -1382 |
| 7 | 245 |
| 8 | -28936 |
| 9 | 131601 |
| 10 | -2444554 |
| 11 | 9399643 |
| 12 | -4727281820 |
| 13 | 1000713051 |
| 14 | -332492454406 |
| 15 | 43079206380025 |
| 16 | -1356840503254192 |
| 17 | 1533724275728365 |
| 18 | -157891629318320864238 |
| 19 | 723708496718865073 |
| 20 | -1044330873985796488204 |