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 | 1 |
| 3 | -5 |
| 4 | -11 |
| 5 | 61 |
| 6 | 211 |
| 7 | -1385 |
| 8 | -6551 |
| 9 | 50521 |
| 10 | 303271 |
| 11 | -2702765 |
| 12 | -19665491 |
| 13 | 199360981 |
| 14 | 1704396331 |
| 15 | -19391512145 |
| 16 | -190473830831 |
| 17 | 2404879675441 |
| 18 | 26684005437391 |
| 19 | -370371188237525 |