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 | -3 |
| 4 | 81 |
| 5 | 5815 |
| 6 | 367791 |
| 7 | 26531589 |
| 8 | 2231306849 |
| 9 | 213451322031 |
| 10 | 21883750567455 |
| 11 | 2048495154903373 |
| 12 | 38238322254619953 |
| 13 | -84508521173113956633 |
| 14 | -48971496478118456699569 |
| 15 | -23204642085706390327411755 |
| 16 | -10849535606183313563987736639 |
| 17 | -5259600981361065001871911307681 |
| 18 | -2687430634156750207499977165012161 |