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 | 3 |
| 2 | -6 |
| 3 | 57 |
| 4 | -294 |
| 5 | 1884 |
| 6 | -13011 |
| 7 | 95178 |
| 8 | -712293 |
| 9 | 5448495 |
| 10 | -42444375 |
| 11 | 335392941 |
| 12 | -2681006280 |
| 13 | 21639853488 |
| 14 | -176113016241 |
| 15 | 1443450932445 |
| 16 | -11903668996713 |
| 17 | 98695838478585 |
| 18 | -822212761531101 |
| 19 | 6878755556938029 |
| 20 | -57767592614370576 |
| 21 | 486792969548157129 |