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 | 4 |
| 4 | 1 |
| 5 | -24 |
| 6 | 50 |
| 7 | -1 |
| 8 | 114 |
| 9 | -950 |
| 10 | 1350 |
| 11 | 31 |
| 12 | -15504 |
| 13 | 400520 |
| 14 | -1897200 |
| 15 | 2052855 |
| 16 | -9269 |
| 17 | 19612560 |
| 18 | -1431859000 |
| 19 | 17333030000 |
| 20 | -56265334125 |
| 21 | 49236404224 |
| 22 | 342953 |
| 23 | -3011508588 |
| 24 | 594221485000 |
| 25 | -16634292228125 |
| 26 | 123422029355625 |
| 27 | -302409994743808 |
| 28 | 222337901418633 |
| 29 | -9945637 |