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 | 0 |
| 4 | 10 |
| 5 | -68 |
| 6 | 818 |
| 7 | -9782 |
| 8 | 130730 |
| 9 | -1835752 |
| 10 | 27408672 |
| 11 | -438578616 |
| 12 | 7697802264 |
| 13 | -150743052528 |
| 14 | 3293454634416 |
| 15 | -78787556904864 |
| 16 | 2014008113598432 |
| 17 | -54001416897306240 |
| 18 | 1504891127666322048 |
| 19 | -43527807706621236480 |
| 20 | 1311515508480252542208 |