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 | 5 |
| 4 | 1 |
| 5 | -35 |
| 6 | 90 |
| 7 | -3 |
| 8 | 595 |
| 9 | -6885 |
| 10 | 12005 |
| 11 | 143 |
| 12 | -150535 |
| 13 | 6175845 |
| 14 | -39484445 |
| 15 | 52245760 |
| 16 | -58201 |
| 17 | 316465625 |
| 18 | -42458934375 |
| 19 | 772604284375 |
| 20 | -3322503800000 |
| 21 | 3547818864576 |
| 22 | 216931 |
| 23 | -6012846875 |
| 24 | 2544269990625 |
| 25 | -120371747505625 |
| 26 | 1294115230100000 |
| 27 | -4145626343257056 |
| 28 | 3713894747640000 |