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 | 0 |
| 5 | -3 |
| 6 | 4 |
| 7 | 25 |
| 8 | -98 |
| 9 | -543 |
| 10 | 4310 |
| 11 | 26980 |
| 12 | -332265 |
| 13 | -2797178 |
| 14 | 42158122 |
| 15 | 524926934 |
| 16 | -7967880874 |
| 17 | -158385569345 |
| 18 | 2011259946668 |
| 19 | 69891223752628 |
| 20 | -565397452159321 |
| 21 | -41784073805527265 |
| 22 | 58655029279732267 |