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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | -6 |
| 5 | 35 |
| 6 | -210 |
| 7 | 1225 |
| 8 | -5670 |
| 9 | -5005 |
| 10 | 750750 |
| 11 | -16391375 |
| 12 | 278528250 |
| 13 | -4130451325 |
| 14 | 51941839950 |
| 15 | -429736682375 |
| 16 | -3328691115750 |
| 17 | 297526876521875 |
| 18 | -10250866397021250 |
| 19 | 276000929009430625 |
| 20 | -6284336658393543750 |
| 21 | 114982352685697371875 |
| 22 | -1137436827419674031250 |