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 | -2 |
| 3 | -3 |
| 4 | -5 |
| 5 | -28 |
| 6 | 67 |
| 7 | 411 |
| 8 | -506 |
| 9 | 10855 |
| 10 | -74231 |
| 11 | -664776 |
| 12 | 7518457 |
| 13 | -30009367 |
| 14 | 1791756790 |
| 15 | 22973709333 |
| 16 | -762305126477 |
| 17 | -10339529833556 |
| 18 | -516074985082229 |
| 19 | -26431010871217485 |
| 20 | 1057255130388472846 |