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 | -3 |
| 5 | 1 |
| 6 | 205 |
| 7 | -4439 |
| 8 | 111021 |
| 9 | -1724351 |
| 10 | 2074717 |
| 11 | 2567577481 |
| 12 | -246042951203 |
| 13 | 14444487376705 |
| 14 | -726562139423955 |
| 15 | 1473171168838825 |
| 16 | 1178164765176836393 |
| 17 | -204468301714665778099 |
| 18 | 138848947223110087743421 |
| 19 | -11701779801284441802592247 |
| 20 | 7774256876827576332115737 |