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 | 0 |
| 4 | 1 |
| 5 | -3 |
| 6 | 13 |
| 7 | -63 |
| 8 | 339 |
| 9 | -1982 |
| 10 | 12429 |
| 11 | -82827 |
| 12 | 582589 |
| 13 | -4303016 |
| 14 | 33240205 |
| 15 | -267697961 |
| 16 | 2241725581 |
| 17 | -19477340744 |
| 18 | 175259713769 |
| 19 | -1630583565434 |
| 20 | 15663877511863 |
| 21 | -155168272246709 |
| 22 | 1583282220672515 |
| 23 | -16623104947488348 |
| 24 | 179409709469784087 |
| 25 | -1988706708427161585 |