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 | -1 |
| 2 | 1 |
| 3 | 5 |
| 4 | -35 |
| 5 | -281 |
| 6 | 5671 |
| 7 | 42671 |
| 8 | -2179127 |
| 9 | -9146017 |
| 10 | 1529743051 |
| 11 | -2876300681 |
| 12 | -1703719191635 |
| 13 | 19006164045023 |
| 14 | 2748187169359087 |
| 15 | -67807538576332801 |
| 16 | -6002760779933693039 |
| 17 | 267196356696377129023 |
| 18 | 16763997717087046669459 |
| 19 | -1258157898725874129675001 |